WO2024111612A1 - Grain-oriented electrical steel sheet - Google Patents

Grain-oriented electrical steel sheet Download PDF

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Publication number
WO2024111612A1
WO2024111612A1 PCT/JP2023/041930 JP2023041930W WO2024111612A1 WO 2024111612 A1 WO2024111612 A1 WO 2024111612A1 JP 2023041930 W JP2023041930 W JP 2023041930W WO 2024111612 A1 WO2024111612 A1 WO 2024111612A1
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Prior art keywords
steel sheet
groove
grain
oriented electrical
grooves
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PCT/JP2023/041930
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French (fr)
Japanese (ja)
Inventor
将嵩 岩城
宣郷 森重
隆史 片岡
春彦 渥美
克 高橋
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日本製鉄株式会社
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Publication of WO2024111612A1 publication Critical patent/WO2024111612A1/en

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/12—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of articles with special electromagnetic properties
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
    • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
    • H01F1/147—Alloys characterised by their composition

Definitions

  • the present invention relates to grain-oriented electrical steel sheets.
  • Grain-oriented electrical steel generally contains 2% to 5% by mass of Si as a steel component, and the crystal grains of the steel are highly concentrated in the ⁇ 110 ⁇ 001> orientation, known as the Goss orientation. Grain-oriented electrical steel has excellent magnetic properties and is used, for example, as the iron core material of stationary inductors in transformers, etc.
  • Grain-oriented electromagnetic steel sheets which are used as the base material for wound transformers, are particularly required to have even lower iron loss. Magnetic domain refinement is performed on electromagnetic steel sheets to reduce iron loss, but wound transformers are annealed to remove distortion during the manufacturing process, so when performing magnetic domain refinement, heat-resistant magnetic domain refinement technology is required.
  • Patent Document 1 describes how, by imparting linear defects to the surface of the steel sheet before or after decarburization annealing, with a spacing of 5 mm or less, a width of 1 mm or less, and a depth of 0.3 to 5.0 ⁇ m in Ra value and 10 ⁇ m or less in Rmax value, a grain-oriented electrical steel sheet with extremely excellent iron loss and coating adhesion can be obtained.
  • Patent Document 2 describes a grain-oriented electrical steel sheet having a steel sheet surface on which grooves are formed that extend in a direction intersecting the rolling direction and whose groove depth direction is the sheet thickness direction.
  • the formed grooves have an asymmetric shape in the groove width direction with respect to the center of the groove width. It is disclosed that an iron loss reduction effect can be obtained by setting the average depth of grooves having such a cross-sectional shape, the arithmetic mean height Ra of the roughness curve that forms the outline of the groove bottom region of the groove, and the average length RSm of the roughness curve elements that form the outline of the groove bottom region within specific ranges.
  • Grain-oriented electrical steel sheets which are used as the base material for wound transformers, are required to have even lower iron loss. Heat-resistant magnetic domain refinement is generally achieved by forming linear grooves, but at present this does not achieve a sufficient iron loss reduction effect.
  • the present invention therefore aims to further reduce the iron loss of grain-oriented electrical steel sheets.
  • the change in the magnetic domain structure during excitation which is related to hysteresis loss, is greatly affected by the movement of the stripe magnetic domains, which are the main magnetic domain structure of grain-oriented electromagnetic steel sheets. If there are no factors that hinder the movement of the magnetic domain walls between the stripe magnetic domains, the movement of the magnetic domain walls (in other words, the movement of the stripe magnetic domains) will be smooth, and hysteresis loss will be reduced.
  • a factor that hinders the movement of the magnetic domain walls is the change in the cross-sectional area of the groove. (Since the groove extends in the length direction, the cross-sectional area may differ between one cross section and another cross section.
  • the cross-sectional area of the front side may differ from that of the back side.
  • the cross section here is a cross section perpendicular to the longitudinal direction or extension direction of the groove.
  • the Ra used in the evaluation of the surface shape (surface roughness) inside the conventional grooves as described in Patent Documents 1 and 2 represents linear roughness, and since the evaluation is typically performed on only one cross section of the groove, the change in the cross-sectional area of the groove (from the front side to the back side of the groove) may not be fully evaluated. Specifically, even if the linear roughness Ra is reduced, the movement of the domain walls does not become smooth, and the hysteresis loss may not be reduced.
  • the inventors have found that by evaluating using the surface roughness Sa instead of the linear roughness Ra, the change in the cross-sectional area of the grooves can be fully evaluated, and by reducing the surface roughness Sa, the movement of the domain walls becomes smooth, and as a result, the hysteresis loss can be reduced.
  • the hysteresis loss can be more reliably reduced by using the surface roughness Sa instead of the conventional linear roughness Ra.
  • the inventors also discovered that in order to form grooves with the desired surface roughness Sa, it is useful to control the manufacturing conditions from the following perspective. That is, by performing pickling treatment using a special pickling solution before forming the grooves, the specific heat and heat transfer coefficient of the precipitates on the steel sheet surface can be made closer to those of the base steel, thereby preventing the groove shape from becoming uneven due to differences in heat transfer.
  • a blower to blow air at a speed of 100 m/s or more when applying a heat source such as laser irradiation, it is possible to prevent components (dust) melted or evaporated from the steel sheet by the heat source from flying up and re-adhering to the steel sheet, laser, etc.
  • the present invention was completed based on the above findings.
  • the iron loss of grain-oriented electrical steel sheets is further reduced by controlling the shape of the linear grooves formed to subdivide the magnetic domains and the Sa value of the surface roughness of the bottom and side surfaces inside the grooves within a certain range.
  • the gist of the present invention is a grain-oriented electrical steel sheet comprising a steel sheet having a surface on which linear grooves extending in a direction forming an angle of 0 to 30° with a rolling perpendicular direction are formed at intervals of 2 to 10 mm, the steel sheet containing, by mass, 2.50 to 4.50% Si, 0.01 to 0.15% Mn, and the balance being Fe and impurities, wherein the groove has a depth D of 10 to 40 ⁇ m, a width W of 20 to 200 ⁇ m, a bottom value Sa of surface roughness of a bottom surface inside the groove being 1.0 to 5.0 ⁇ m, and a side value Sa of surface roughness of a side surface inside the groove being 1.0 to 5.0 ⁇ m.
  • the surface roughness Sa inside the formed groove is limited to a predetermined range, which allows the magnetic domain walls to move smoothly, reducing hysteresis loss and, as a result, iron loss.
  • FIG. 1 is a cross-sectional view of a groove in a grain-oriented electrical steel sheet according to the present invention.
  • the steel sheet used in the grain-oriented electrical steel sheet of the present invention contains components that are favorable for controlling the crystal orientation to a texture concentrated in the ⁇ 110 ⁇ 001> orientation (Goss orientation), and contains at least Si: 2.50-4.50% and Mn: 0.01-0.15%.
  • Si The content of Si (silicon) is 2.50 to 4.50%. Si increases the electrical resistance of the steel sheet, thereby reducing eddy current loss, which is one of the causes of iron loss. If the content of Si is less than 2.50%, it is not preferable because it becomes difficult to sufficiently suppress the eddy current loss of the final grain-oriented electrical steel sheet. If the content of Si is more than 4.50%, it is not preferable because the workability of the grain-oriented electrical steel sheet decreases. Therefore, the content of Si is 2.50 to 4.50%, and preferably 2.70 to 4.00%.
  • Mn 0.01 to 0.15%
  • Mn forms MnS and MnSe, which are inhibitors that affect secondary recrystallization. If the content of Mn is less than 0.01%, the absolute amount of MnS and MnSe that cause secondary recrystallization is insufficient, which is not preferable. If the content of Mn is more than 0.15%, it is not preferable because it becomes difficult to dissolve Mn during slab heating. In addition, if the content of Mn is more than 0.15%, the precipitation size of MnS and MnSe, which are inhibitors, tends to become coarse, which is not preferable because the optimal size distribution as an inhibitor is impaired. Therefore, the content of Mn is 0.01 to 0.15%, preferably 0.03 to 0.13%.
  • the components other than Si and Mn may be the components contained in ordinary grain-oriented electrical steel sheets.
  • components other than Si and Mn the following may be contained in mass %: C: up to 0.085%, acid-soluble Al: up to 0.065%, N: up to 0.012%, Cr: up to 0.30%, Cu: up to 0.400%, P: up to 0.500%, Sn: up to 0.300%, Sb: up to 0.300%, Ni: up to 1.000%, S: up to 0.015%, Se: up to 0.015%, and Bi: up to 0.020%.
  • the contents of these components are the contents in the final product that has been subjected to purification annealing and the like, so the lower limit is not limited and may be 0%.
  • the remainder of the steel plate other than the above components is Fe and impurities.
  • impurity elements refer to components contained in the raw materials or components mixed in during the manufacturing process, but not intentionally included in the steel plate.
  • grooves are formed on the surface of the steel sheet, which extend in a direction intersecting the rolling direction and whose depth direction is the sheet thickness direction.
  • the grooves need not necessarily be perpendicular to the rolling direction as long as they are provided so as to intersect with the rolling direction, but are provided in a direction that forms an angle of 0 to 30° with the direction perpendicular to the rolling direction.
  • the grooves do not necessarily have to have a linear shape when viewed from the sheet thickness direction (when the grooves are viewed from above), and may have an arched shape.
  • the groove shape described below is measured after removing at least the glass coating and insulating coating from the inside of the groove from the final product by pickling or the like.
  • the grooves may include the inside of the groove, and the inside of the groove refers to the area defined by the contour of the groove and recessed from the surface of the steel sheet. As described below, the grooves may include the wall surfaces (also called side surfaces) and the bottom surface of the inside of the groove.
  • the grooves are formed on the surface of the steel sheet at intervals of 2 to 10 mm. If the groove spacing is less than 2 mm, the magnetic domain refinement effect saturates, making it difficult to obtain a reduction in eddy current loss, while hysteresis loss increases due to distortion, resulting in an increase in iron loss, which is undesirable. If the groove spacing exceeds 20 mm, the magnetic domain refinement effect decreases, resulting in insufficient iron loss improvement, which is undesirable.
  • the preferred groove spacing is 3 to 7 mm.
  • FIG. 1 is a cross-sectional view of a groove in an electromagnetic steel sheet of the present invention.
  • the inside of the groove is shaped like a trapezoid, but the shape of the inside of the groove may also be arched.
  • the depth D of the groove is in the range of 10 ⁇ m to 40 ⁇ m. If the depth D is less than 10 ⁇ m, the amount of magnetic poles generated from the wall surface inside the groove (sometimes referred to as the side surface inside the groove) is small, and sufficient iron loss reduction effect cannot be obtained. If the depth D exceeds 40 ⁇ m, the magnetic domains are subdivided, but the reduction in magnetic flux density due to the formation of the groove is large, and sufficient magnetic properties may not be obtained.
  • the preferred depth is 15 ⁇ m to 30 ⁇ m.
  • the method for measuring the "depth D" according to the present invention is as follows. An arbitrary groove in the electromagnetic steel sheet was selected, and the maximum depths of two arbitrary points (A) and (B) of the groove, which are 3 mm apart on the front side and the back side in the extension direction of the groove as shown in the cross-sectional view of the groove in Figure 1, were measured using a laser microscope (a 3D laser microscope using a confocal optical system with a pinhole), with the deeper one being depth d and the shallower one being depth d'. Depth D is the average value of these values.
  • the "groove width W" in this invention refers to the portions indicated by w and w' in Figure 1.
  • the groove width W is in the range of 20 ⁇ m to 200 ⁇ m. If the width W is less than 20 ⁇ m, magnetic flux leaking from the wall surface inside the groove (side surface inside the groove) enters the wall surface inside the groove on the opposite side (side surface inside the groove), reducing the amount of magnetic pole generated and not achieving a sufficient iron loss reduction effect. If the width W exceeds 200 ⁇ m, the iron loss reduction effect saturates, and the laser power required to form the groove increases, resulting in increased manufacturing costs.
  • the preferred width W is 30 to 100 ⁇ m.
  • the method for measuring the "groove width W" is as follows. An arbitrary groove of the electromagnetic steel sheet was selected, and the widths of the widths at which the depths of the grooves at two arbitrary points (A) and (B) located 3 mm apart on the front and back sides in the extension direction of the grooves, respectively, are half of the maximum depths d and d' of the respective grooves, were measured using a laser microscope (a 3D laser microscope using a pinhole confocal optical system), with the wider width being w and the narrower width being w', as shown in the cross-sectional view of the groove in Figure 1.
  • the groove width W is the average value of these values.
  • the “surface roughness Sa value of the bottom surface and the side surface of the groove” in the present invention refers to the arithmetic mean height Sa of the surface (three-dimensional surface) roughness of the bottom surface and the side surface of the groove between two points (A) and (B) in FIG. 1.
  • the surface roughness of the bottom surface of the groove may be referred to as Sa bottom
  • the surface roughness of the side surface of the groove may be referred to as Sa side .
  • each Sa is 1.0 to 5.0 ⁇ m, preferably 1.5 to 4.0 ⁇ m, and more preferably 2.0 to 3.0 ⁇ m.
  • the reason that the effect of reducing iron loss is obtained by setting the surface roughness Sa of the bottom surface and side surfaces inside the groove within the range of 1.0 to 5.0 ⁇ m is believed to be that the surface roughness being within a specified range (the change in the cross-sectional area of the groove from the front to the back in the extension direction of the groove is suppressed), smooths the movement of the magnetic domain walls and suppresses the increase in hysteresis loss.
  • the unevenness of the bottom surface inside the groove is the surface roughness Sa bottom of the bottom surface inside the groove of the present invention.
  • the range of one side width 0.5 ⁇ m (both widths 1.0 ⁇ m) in the perpendicular direction (and in the thickness direction of the electromagnetic steel sheet) from the straight line connecting the points on the same side of the maximum depth is defined as the side inside the groove, and Sa left and Sa right of the unevenness of the side inside the groove are derived, and the average value of these values is defined as Sa side of the side inside the groove.
  • the linear surface roughness Ra value of the bottom surface inside the groove and the side surface inside the groove refers to the arithmetic mean height Ra of the roughness curve of the bottom surface inside the groove and the side surface inside the groove between two points (A) and (B) in Figure 1.
  • the definition of the arithmetic mean height Ra of the roughness curve follows Japanese Industrial Standard JIS B 0601 (2013).
  • the hot-rolled steel sheet is pickled to obtain a pickled sheet, or the hot-rolled steel sheet is annealed to obtain a hot-rolled annealed sheet, and then the hot-rolled annealed sheet is pickled to obtain a pickled sheet.
  • the pickling solution used here contains one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn, and Ni, the total concentration of each element is 0.0001 to 0.1000 mass% or less with respect to the pickling solution, and the pH is -1 to 5.
  • the temperature of the pickling solution is 15°C to 100°C, and the time for which the steel sheet is immersed in the pickling solution is 5 seconds to 200 seconds. A pickled sheet is obtained by this pickling process, and the pickled sheet is cold-rolled to obtain a cold-rolled steel sheet.
  • the components of the slab used in the production of the grain-oriented electrical steel sheet according to the present invention contain at least Si: 2.50 to 4.50%, Mn: 0.01 to 0.15%.
  • the Si (silicon) content is 2.50-4.50%. Si increases the electrical resistance of the steel sheet, thereby reducing eddy current loss, which is one of the causes of iron loss. If the Si content is less than 2.50%, it is not preferable because it becomes difficult to sufficiently suppress eddy current loss in the final grain-oriented electrical steel sheet. If the Si content is more than 4.50%, it is not preferable because the workability of the grain-oriented electrical steel sheet decreases. Therefore, the Si content is 2.50%-4.50%, and preferably 2.70-4.00%.
  • the Mn (manganese) content is 0.01 to 0.15%. Mn forms MnS and MnSe, which are inhibitors that affect secondary recrystallization. If the Mn content is less than 0.01%, the absolute amount of MnS and MnSe that cause secondary recrystallization is insufficient, which is undesirable. If the Mn content is more than 0.15%, it is undesirable because it becomes difficult for Mn to form a solid solution when the slab is heated. Also, if the Mn content is more than 0.15%, it is undesirable because the precipitate size of MnS and MnSe, which are inhibitors, tends to become coarse, which impairs the optimal size distribution as an inhibitor. Therefore, the Mn content is 0.01 to 0.15%, and preferably 0.03 to 0.13%.
  • the components other than Si and Mn can be the following components.
  • the alloy may contain, in mass %, C: 0.020 to 0.100%, one or two of S and Se: 0.001 to 0.050%, acid-soluble Al: 0.010 to 0.050%, N: 0.002 to 0.015%, Cr: up to 0.30% or less, Cu: up to 0.400% or less, P: up to 0.500% or less, Sn: up to 0.300% or less, Sb: up to 0.300% or less, Ni: up to 1.000% or less, and Bi: up to 0.020% or less.
  • the C (carbon) content is 0.020-0.100%.
  • C has various roles, but if the C content is less than 0.020%, the grain size becomes excessively large when the slab is heated, which increases the iron loss value of the final grain-oriented electrical steel sheet, which is not preferable. If the C content exceeds 0.100%, the decarburization time becomes long during decarburization after cold rolling, which increases the manufacturing cost, which is not preferable. Also, if the C content exceeds 0.100%, decarburization is likely to be incomplete, which is not preferable because it may cause magnetic aging in the final grain-oriented electrical steel sheet. Therefore, the C content is 0.020-0.100%, and preferably 0.050-0.090%.
  • the total content of S (sulfur) and Se (selenium) is 0.001-0.050%.
  • S and Se form inhibitors together with the above-mentioned Mn. Both S and Se may be contained in the slab, but it is sufficient that at least one of them is contained in the slab. If the total content of S and Se is outside the above range, it is not preferable because a sufficient inhibitor effect cannot be obtained. Therefore, the total content of S and Se is 0.001-0.050%, and preferably 0.001-0.040%.
  • the acid-soluble Al (acid-soluble aluminum) content is 0.010-0.050%.
  • Acid-soluble Al constitutes an inhibitor necessary for producing grain-oriented electrical steel sheets with high magnetic flux density. If the acid-soluble Al content is less than 0.010%, the amount of acid-soluble Al is insufficient, and the inhibitor strength is insufficient, which is not preferable. If the acid-soluble Al content is more than 0.050%, the AlN that precipitates as an inhibitor becomes coarse, which is not preferable, as it reduces the inhibitor strength. Therefore, the acid-soluble Al content is 0.010-0.050%, and preferably 0.010-0.040%.
  • the N (nitrogen) content is 0.002-0.015%. N forms AlN, an inhibitor, together with the acid-soluble Al mentioned above. If the N content is outside the above range, it is not preferable because a sufficient inhibitor effect cannot be obtained. Therefore, the N content is 0.002-0.015%, and preferably 0.002-0.012%.
  • the slab used in the manufacture of the grain-oriented electrical steel sheet according to this embodiment may contain, in mass%, one or more elements selected from the group consisting of Cu: 0.400% or less, P: 0.500% or less, Sn: 0.300% or less, Sb: 0.300% or less, Ni: 1.000% or less, S: 0.025% or less, Se: 0.025% or less, and Bi: 0.020% or less, in place of a portion of the remaining Fe, in order to improve magnetic properties.
  • the Cr content may be 0.02% or more
  • the Bi content may be 0.0005% or more
  • the Sb content may be 0.005% or more
  • the Se content may be 0.001% or more
  • the Mo content may be 0.005% or more, in mass%.
  • a slab is formed by casting molten steel adjusted to the composition described above.
  • the method of casting the slab is not particularly limited. In research and development, even if a steel ingot is formed in a vacuum melting furnace or the like, the same effects can be confirmed for the above-mentioned components as when a slab is formed.
  • a leveller or the like can be used in addition to shot blasting.
  • the conditions for shot blasting include, for example, using a mechanical projector to project 1,000 kg of iron balls with a hardness of about Hv500 and a diameter of about 1.5 mm at a projection speed of 50 m/s per minute, but there are no restrictions as long as fine cracks are introduced into the steel plate that allow the pickling solution to penetrate.
  • the processed hot-rolled steel sheet is pickled or hot-rolled sheet annealed to obtain a hot-rolled annealed sheet, which is then pickled.
  • the pickling solution contains one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni, the total concentration of each element is 0.0001-0.1000 mass% of the pickling solution, and the pH is -1 or more and 5 or less.
  • the temperature of the pickling solution is 15°C or more and 100°C or less, and the steel sheet is immersed in the pickling solution for 5 seconds or more and 200 seconds or less.
  • the total concentration of one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni in the pickling solution is less than 0.0001% by mass, the effect of inhibitor control in the thickness direction (substituting or coating MnS, etc. with CuS, etc.) becomes insufficient, which is not preferable. If the total concentration of one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni in the pickling solution exceeds 0.1000% by mass, the effect of improving magnetic properties becomes saturated and the cost of the pickling solution increases, which is not preferable. Therefore, the total concentration of one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni in the pickling solution is 0.0001 to 0.1000% by mass.
  • the pH of the pickling solution is less than -1, it is undesirable because the acidity becomes too strong and the solution becomes difficult to handle. If the pH of the pickling solution is more than 5, the effect of the pickling process in controlling inhibitors in the thickness direction becomes insufficient, which is undesirable. Therefore, the pH of the pickling solution is between -1 and 5.
  • the temperature of the pickling solution is less than 15°C, the effect of the pickling process in controlling inhibitors in the thickness direction will be insufficient, which is not preferable. If the temperature of the pickling solution is more than 100°C, it will be difficult to handle the pickling solution, which is also not preferable. Therefore, the temperature of the pickling solution should be 15°C or higher and 100°C or lower.
  • the time during which the steel sheet is immersed in the pickling solution during the pickling process is less than 5 seconds, the effect of the pickling process in controlling inhibitors in the thickness direction will be insufficient, which is not preferable. If the time during which the steel sheet is immersed in the pickling solution during the pickling process exceeds 200 seconds, the equipment will become long and large, which is not preferable. Therefore, the time during which the steel sheet is immersed in the pickling solution during the pickling process is 5 seconds or more and 200 seconds or less.
  • the precipitates in the steel such as MnS
  • CuS copper
  • the heat transfer coefficient of the steel sheet surface containing the precipitates can be made constant. This makes it possible to make the effect of heat from laser irradiation, etc., constant when forming grooves.
  • the precipitates are not sufficiently replaced or coated by pickling, there will be large variations in the heat transfer coefficient of the steel sheet surface, and the surface roughness Sa of the bottom and side surfaces inside the grooves will increase.
  • the pickling time or pickling solution concentration is set to a certain level or higher, the effect of stabilizing the heat transfer coefficient will saturate and no further reduction in Sa can be expected.
  • the hot-rolled steel sheet is subjected to pickling and then rolled by one cold rolling or multiple cold rolling with intermediate annealing therebetween to be processed into a cold-rolled steel sheet.
  • the steel sheet may be heat-treated at about 300° C. or less between passes of cold rolling, between rolling roll stands, or during rolling. In such a case, the magnetic properties of the final grain-oriented electrical steel sheet can be improved.
  • the hot-rolled steel sheet may be rolled by three or more cold rolling passes, but since multiple cold rolling passes increase the manufacturing cost, it is preferable to roll the hot-rolled steel sheet by one or two cold rolling passes.
  • each cold rolling pass is not particularly limited, but is preferably 9 passes or less from the viewpoint of manufacturing costs.
  • the process for obtaining a cold-rolled steel sheet from a slab has been described above.
  • decarburization annealing is performed.
  • the cold-rolled steel sheet is subjected to heat treatment (i.e., decarburization annealing) under a predetermined temperature condition (for example, heating at 700 to 900°C for 1 to 3 minutes).
  • a predetermined temperature condition for example, heating at 700 to 900°C for 1 to 3 minutes.
  • the carbon in the cold-rolled steel sheet is reduced to a predetermined amount or less, and a primary recrystallization structure is formed.
  • an oxide layer containing silica (SiO 2 ) as a main component is formed on the surface of the cold-rolled steel sheet.
  • an annealing separator is applied to the surface of the cold-rolled steel sheet (the surface of the oxide layer).
  • the cold-rolled steel sheet coated with the annealing separator is subjected to heat treatment (i.e., finish annealing) under a predetermined temperature condition (for example, heating at 1100 to 1300°C for 20 to 24 hours).
  • finish annealing is performed, secondary recrystallization occurs in the cold-rolled steel sheet and the cold-rolled steel sheet is purified.
  • a steel sheet is obtained that has the above-mentioned chemical composition of the steel sheet and has a crystal orientation controlled so that the magnetization easy axis of the crystal grains coincides with the rolling direction X.
  • the oxide layer containing silica as a main component reacts with the annealing separator containing magnesia as a main component to form a glass film containing composite oxides such as forsterite ( Mg2SiO4 ) on the surface of the steel sheet.
  • the finish annealing treatment is performed with the steel sheet wound in a coil shape. The formation of a glass film on the surface of the steel sheet during the finish annealing treatment can prevent the occurrence of seizure on the coiled steel sheet.
  • Step of forming linear grooves on steel sheet surface In the subsequent laser irradiation process, a laser is irradiated onto the surface (only one side) of the steel plate on which the glass coating has been formed, to form a plurality of grooves on the surface of the steel plate extending in a direction intersecting the rolling direction at intervals of 2 to 10 mm along the rolling direction.
  • the laser irradiation device rotates a polygon mirror to irradiate the surface of the steel plate with laser light, and scans the laser light in a direction that forms an angle of 0 to 30 degrees with the direction perpendicular to the rolling direction.
  • an assist gas such as air or an inert gas is sprayed onto the portion of the steel sheet to be irradiated with the laser light.
  • the inert gas is, for example, nitrogen or argon.
  • the assist gas plays a role in removing the components melted or evaporated from the steel sheet by the laser irradiation. By spraying the assist gas, the laser light reaches the steel sheet without being hindered by the melted or evaporated components, so that the grooves are formed generally stably.
  • the assist gas is blown only onto the laser irradiation spot, the components (dust) melted or evaporated from the steel sheet generated inside the groove are blown up into the assist gas, and although there is an action of preventing the components from remaining inside the groove, it is difficult to prevent re-adhesion to the steel sheet, laser, etc. outside the groove. This may cause the surface roughness Sa of the bottom and side surfaces of the groove to fluctuate, and the desired surface roughness Sa may not be obtained. In order to prevent such re-adhesion, blower gas is used to move the dust removed outside the groove away from the steel sheet.
  • a blower is used to blow air at a speed of 100 m/s or more and 200 m/s or less onto the laser irradiation surface during laser irradiation.
  • the effect of suppressing re-adhesion is insufficient, and at more than 200 m/s, the steel sheet vibrates due to the wind.
  • grooves having the desired surface roughness Sa are formed.
  • the laser light source for example, a high-power laser generally used for industrial purposes, such as a fiber laser, a YAG laser, a semiconductor laser, or a CO2 laser, can be used.
  • a pulsed laser or a continuous wave laser may be used as the laser light source as long as it can stably form a groove.
  • the laser light it is preferable to use a single mode laser that has high light-collecting ability and is suitable for forming a groove.
  • the laser light irradiation conditions for example, it is preferable to set the laser output to 200W to 3000W, the focused spot diameter of the laser light in the rolling direction (i.e. the diameter containing 86% of the laser output, hereinafter abbreviated as 86% diameter) to 10 ⁇ m to 200 ⁇ m, the focused spot diameter of the laser light in the plate width direction (86% diameter) to 10 ⁇ m to 1000 ⁇ m, the laser scanning speed to 5m/s to 50m/s, and the laser scanning pitch (spacing PL) to 2mm to 10mm.
  • the laser irradiation conditions are adjusted appropriately so that a groove depth D of 10 to 40 ⁇ m is obtained.
  • an insulating coating liquid containing, for example, colloidal silica and phosphate is applied from above the glass film to the steel sheet surface on which grooves have been formed by the above-mentioned laser irradiation.
  • Heat treatment is then carried out under specified temperature conditions (for example, 840 to 920°C), ultimately obtaining the steel sheet on which grooves have been formed, the glass film, and the insulating film according to the present invention.
  • the groove depth D, groove width W, and surface roughness Sa of the bottom and side surfaces inside the groove were measured for the shape of the grooves formed in the obtained grain-oriented electrical steel sheet using the measurement method described above.
  • the grain-oriented electrical steel sheet of the present invention will be described in more detail, showing examples. Note that the examples shown below are merely examples of the grain-oriented electrical steel sheet according to this embodiment, and the grain-oriented electrical steel sheet according to this embodiment is not limited to the examples shown below.
  • the grain-oriented electrical steel sheet contained, by mass fraction, Si: 3.00%, C: 0.080%, acid-soluble Al: 0.050%, N: 0.010%, Mn: 0.12%, Cr: 0.05%, Cu: 0.040%, P: 0.010%, Sn: 0.020%, Sb: 0.010%, Ni: 0.005%, S: 0.007%, Se: 0.001%, with the remainder being Fe and impurities.
  • the slab was then hot-rolled to obtain a hot-rolled steel sheet having a thickness of 2.3 mm.
  • the hot-rolled steel sheets were annealed at 1000°C for 1 minute.
  • the surface of the shot-blasted hot-rolled steel sheet was pickled using the pickling solution and conditions shown below, and then cold-rolled to obtain a cold-rolled steel sheet with a thickness of 0.23 mm.
  • this cold-rolled steel sheet was subjected to a decarburization annealing process under temperature conditions of heating at 800°C for 2 minutes, and then an annealing separator containing magnesia (MgO) as its main component was applied to the surface of the cold-rolled steel sheet.
  • MgO magnesia
  • the pickling solution contains one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni, with the total concentration of each element being 0.0001 to 0.1000 mass% based on the mass of the pickling solution.
  • pH value -1 to 5
  • Tempoture 15°C to 100°C
  • Immersion time 5 seconds to 200 seconds
  • the cold-rolled steel sheet coated with the annealing separator was subjected to a final annealing process under the temperature conditions of heating at 1200°C for 20 hours.
  • a steel sheet was obtained with the above-mentioned chemical composition, a glass film formed on the surface, and a crystal orientation controlled so that the magnetization easy axis of the crystal grains coincided with the rolling direction.
  • a laser was irradiated onto the surface of the steel plate on which the glass film had been formed, forming multiple grooves on the surface of the steel plate that extended in a direction intersecting the rolling direction and at predetermined intervals along the rolling direction.
  • the conditions for the laser light irradiation were adjusted so that the desired groove depth D was obtained, with a laser output in the range of 200 W to 3000 W, a focused spot diameter (86% diameter) of the laser light in the rolling direction in the range of 10 ⁇ m to 500 ⁇ m, a focused spot diameter (86% diameter) of the laser light in the plate width direction in the range of 10 ⁇ m to 1000 ⁇ m, a laser scanning speed in the range of 5 m/s to 50 m/s, and a laser scanning pitch (spacing PL) in the range of 2 mm to 10 mm.
  • a laser output in the range of 200 W to 3000 W
  • a focused spot diameter (86% diameter) of the laser light in the rolling direction in the range of 10 ⁇ m to 500 ⁇ m
  • a focused spot diameter (86% diameter) of the laser light in the plate width direction in the range of 10 ⁇ m to 1000 ⁇ m
  • a laser scanning speed in the range of 5 m/s to 50 m/s
  • a blower when a laser was irradiated onto a steel sheet, a blower was used to blow air at a speed of 100 m/s or more onto the laser irradiated surface of the steel sheet in the TD direction (sheet width direction) of the steel sheet and in a direction as parallel as possible to the steel sheet surface, thereby preventing components melted or evaporated from the steel sheet by laser irradiation from flying up and re-adhering to the steel sheet, the laser, etc.
  • an insulating coating liquid containing colloidal silica and phosphate was applied to the steel sheet with grooves on top of the glass film, and then heat treatment was carried out under temperature conditions of 850°C for 1 minute, ultimately resulting in a grain-oriented electrical steel sheet with grooves, a glass film, and an insulating film.
  • the groove shape was measured using the measurement method described above, including groove depth D, groove width W, and surface roughness Sa of the bottom and side surfaces inside the groove.
  • the measurement results are shown in Table 1 along with the linear roughness Ra and iron loss W17/50.
  • Good iron loss W17/50 is set to 0.73 (W/kg) or less, and those that meet this standard were marked with a circle (Good). Iron loss was measured in accordance with JIS C2556:2015.

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Abstract

The present invention further reduces iron loss in an obtained grain-oriented electrical steel sheet by controlling the shape of a linear groove formed for magnetic domain refinement and controlling the Sa values for the surface roughness of the bottom surface of the groove interior and the side surfaces of the groove interior to be within a fixed range.　Provided is a grain-oriented electrical steel sheet comprising a steel sheet that contains, in mass%, 2.50-4.50% of Si and 0.01-0.15% of Mn, with the remainder comprising Fe and impurities, and that has a steel sheet surface in which linear grooves extending in a direction forming an angle of 0-30° relative to a direction orthogonal to the rolling direction are formed at intervals of 2-10 mm, wherein the depth D of the grooves is 10-40 μm, the width W of the grooves is 20-200 μm, the Sabottom value for the roughness of the bottom surface of the groove interior is 1.0-5.0 μm, and the Saside value for the roughness of the side surfaces of the groove interior is 1.0-5.0 μm.

Description

方向性電磁鋼板Grain-oriented electrical steel sheet
　本発明は、方向性電磁鋼板に関する。 The present invention relates to grain-oriented electrical steel sheets.
　方向性電磁鋼板は、鋼板成分として、一般的に、Ｓｉを２質量％～５質量％程度含有し、鋼板の結晶粒の方位をＧｏｓｓ方位と呼ばれる｛１１０｝＜００１＞方位に高度に集積させた鋼板である。方向性電磁鋼板は、磁気特性に優れ、例えば、変圧器等の静止誘導器の鉄心材料などとして利用される。 Grain-oriented electrical steel generally contains 2% to 5% by mass of Si as a steel component, and the crystal grains of the steel are highly concentrated in the {110}<001> orientation, known as the Goss orientation. Grain-oriented electrical steel has excellent magnetic properties and is used, for example, as the iron core material of stationary inductors in transformers, etc.
　このような方向性電磁鋼板では、磁気特性を向上させるために、種々の技術開発がなされている。特に、近年の省エネルギー化の要請に伴って、方向性電磁鋼板では、さらなる低鉄損化が求められている。方向性電磁鋼板の低鉄損化には、鋼板の結晶粒の方位について、Ｇｏｓｓ方位への集積度を高めて磁束密度を向上させて、ヒステリシス損失を低減することが有効である。 In order to improve the magnetic properties of such grain-oriented electrical steel sheets, various technological developments have been made. In particular, with the recent demand for energy conservation, there is a demand for further reduction in iron loss in grain-oriented electrical steel sheets. To reduce iron loss in grain-oriented electrical steel sheets, it is effective to increase the concentration of crystal grains in the Goss orientation in the steel sheet, improve magnetic flux density, and reduce hysteresis loss.
　巻トランスの母材として用いられる方向性電磁鋼板には、特に、更なる低鉄損化が求められている。電磁鋼板では、低鉄損化の為に磁区細分化を行っているが、巻トランスでは製造工程で歪み取り焼鈍を行う為、磁区細分化を行う場合、耐熱型の磁区細分化技術が必要である。 Grain-oriented electromagnetic steel sheets, which are used as the base material for wound transformers, are particularly required to have even lower iron loss. Magnetic domain refinement is performed on electromagnetic steel sheets to reduce iron loss, but wound transformers are annealed to remove distortion during the manufacturing process, so when performing magnetic domain refinement, heat-resistant magnetic domain refinement technology is required.
　耐熱型の磁区細分化手法として鋼板に周期的な溝を形成する手法がある。例えば、特許文献１には、脱炭焼鈍前又は後の鋼板表面に、間隔５ｍｍ以下、幅１ｍｍ以下、深さがＲａ値で０．３～５．０μｍ且つＲｍａｘ値で１０μｍ以下の線状疵を付与することで、極めて鉄損が優れ、被膜密着性の優れた方向性電磁鋼板が得られることが記載されている。 One method for heat-resistant magnetic domain refinement is to form periodic grooves in steel sheet. For example, Patent Document 1 describes how, by imparting linear defects to the surface of the steel sheet before or after decarburization annealing, with a spacing of 5 mm or less, a width of 1 mm or less, and a depth of 0.3 to 5.0 μm in Ra value and 10 μm or less in Rmax value, a grain-oriented electrical steel sheet with extremely excellent iron loss and coating adhesion can be obtained.
　特許文献２には、圧延方向と交差する方向に延在し且つ溝深さ方向が板厚方向となる溝が形成された鋼板表面を有する方向性電磁鋼板が記載されている。形成されている溝は、溝幅方向において前記溝幅中心を基準として非対称形状である。このような断面形状を有する溝の平均深さ、溝の溝底領域の輪郭を成す粗さ曲線の算術平均高さＲａ、溝底領域の前記輪郭を成す粗さ曲線要素の平均長さＲＳｍを特定の範囲にすることにより、鉄損低減効果が得られることが開示されている。 Patent Document 2 describes a grain-oriented electrical steel sheet having a steel sheet surface on which grooves are formed that extend in a direction intersecting the rolling direction and whose groove depth direction is the sheet thickness direction. The formed grooves have an asymmetric shape in the groove width direction with respect to the center of the groove width. It is disclosed that an iron loss reduction effect can be obtained by setting the average depth of grooves having such a cross-sectional shape, the arithmetic mean height Ra of the roughness curve that forms the outline of the groove bottom region of the groove, and the average length RSm of the roughness curve elements that form the outline of the groove bottom region within specific ranges.
特開平１－１９８４２９号公報Japanese Patent Application Laid-Open No. 1-198429 再表２０１６－１７１１３０号公報Republished Publication No. 2016-171130
　巻トランスの母材として用いられる方向性電磁鋼板には、更なる低鉄損化が求められている。耐熱型の磁区細分化は一般的には、線状の溝を形成することによって行われているが、現状では十分な鉄損低減効果は得られていない。 Grain-oriented electrical steel sheets, which are used as the base material for wound transformers, are required to have even lower iron loss. Heat-resistant magnetic domain refinement is generally achieved by forming linear grooves, but at present this does not achieve a sufficient iron loss reduction effect.
　そこで、本発明は、方向性電磁鋼板の鉄損を更に低減することを目的とする。 The present invention therefore aims to further reduce the iron loss of grain-oriented electrical steel sheets.
　線状の溝の形成では十分な鉄損低減効果は得られていない理由として、溝の形成により磁区細分化され渦電流損が低減する一方で、溝の形成による溝の表面粗さ（表面粗度ともいう）が増加しヒステリシス損が増加するため、と本発明者らは考えた。 The inventors believe that the reason why forming linear grooves does not sufficiently reduce iron loss is that while the formation of the grooves subdivides the magnetic domains and reduces eddy current loss, the formation of the grooves increases the surface roughness (also called surface roughness) of the grooves, which increases hysteresis loss.
　ヒステリシス損に関連する、励磁時の磁区構造の変化は、方向性電磁鋼板の主磁区構造であるストライプ磁区の移動に大きく影響を受ける。ストライプ磁区の間の磁壁の移動を阻害する要因が無い場合には磁壁の移動（言い換えるとストライブ磁区の移動）がスムーズになり、ヒステリシス損が低減される。ここで、磁壁の移動を阻害する要因として溝の断面積の変化があげられる。（溝は、長さ方向に延在しているので、或る断面と別の断面では、断面積が異なることがある。例えば、手前側から奥側に延在する溝では、手前側の断面と奥側の断面で、断面積が異なることがある。ここでの断面とは、溝の長手方向または延在方向に対して垂直な断面である。）溝の断面積が変化しない、すなわち溝の手前側から奥側まで溝断面の投影形状が均一であるほど、言い換えると溝内部の表面粗さが小さいほど、磁壁の移動はスムーズになる、と考えられる。 The change in the magnetic domain structure during excitation, which is related to hysteresis loss, is greatly affected by the movement of the stripe magnetic domains, which are the main magnetic domain structure of grain-oriented electromagnetic steel sheets. If there are no factors that hinder the movement of the magnetic domain walls between the stripe magnetic domains, the movement of the magnetic domain walls (in other words, the movement of the stripe magnetic domains) will be smooth, and hysteresis loss will be reduced. Here, a factor that hinders the movement of the magnetic domain walls is the change in the cross-sectional area of the groove. (Since the groove extends in the length direction, the cross-sectional area may differ between one cross section and another cross section. For example, in a groove that extends from the front side to the back side, the cross-sectional area of the front side may differ from that of the back side. The cross section here is a cross section perpendicular to the longitudinal direction or extension direction of the groove.) It is thought that the more the cross-sectional area of the groove does not change, that is, the more uniform the projected shape of the groove cross section from the front side to the back side of the groove, in other words, the smaller the surface roughness inside the groove, the smoother the movement of the magnetic domain walls will be.
　ここで、特許文献１～２に記載されるような従来の溝内部の表面形状（表面粗さ）の評価で用いられていたＲａは、線形の粗さを表しており、典型的には溝の一断面だけで評価をしているので、（溝の手前側から奥側までの）溝の断面積の変化を十分に評価することができないことがある。具体的には、線形粗さＲａを小さくしても磁壁の移動がスムーズにならず、ヒステリシス損が低減しないことがあった。これに対して、本発明者らは、線形の粗さＲａに代えて、面の粗さＳａで評価することにより、溝の断面積の変化を十分に評価することができ、面の粗さＳａを小さくすることで磁壁の移動がスムーズになり、その結果ヒステリシス損を低減できることを知見した。つまり、溝内部の表面形状（表面粗さ）を評価する際に、従来の線形粗さＲａではなく面の粗さＳａを用いることにより、より確実にヒステリシス損を低減することができる。 Here, the Ra used in the evaluation of the surface shape (surface roughness) inside the conventional grooves as described in Patent Documents 1 and 2 represents linear roughness, and since the evaluation is typically performed on only one cross section of the groove, the change in the cross-sectional area of the groove (from the front side to the back side of the groove) may not be fully evaluated. Specifically, even if the linear roughness Ra is reduced, the movement of the domain walls does not become smooth, and the hysteresis loss may not be reduced. In response to this, the inventors have found that by evaluating using the surface roughness Sa instead of the linear roughness Ra, the change in the cross-sectional area of the grooves can be fully evaluated, and by reducing the surface roughness Sa, the movement of the domain walls becomes smooth, and as a result, the hysteresis loss can be reduced. In other words, when evaluating the surface shape (surface roughness) inside the grooves, the hysteresis loss can be more reliably reduced by using the surface roughness Sa instead of the conventional linear roughness Ra.
　また、本発明者らは、所望の表面粗さＳａを有する溝を形成するために、製造条件を次の観点から制御することが有用であることも見出した。すなわち、溝の形成の前に特殊な酸洗溶液を用いて酸洗処理をすることで、鋼板表面の析出物の比熱、伝熱係数を地鉄の比熱、伝熱係数と近づけることにより、伝熱の違いによる、溝の形状の不均一化を予防できること、加えて、レーザー照射等の熱源印加時にブロワーを用いて１００ｍ／ｓ以上の風速で風を送ることにより、熱源によって鋼板から溶融又は蒸発した成分（ダスト）が舞い上がって、鋼板やレーザーなどへの再付着することを抑制できることを見出した。 The inventors also discovered that in order to form grooves with the desired surface roughness Sa, it is useful to control the manufacturing conditions from the following perspective. That is, by performing pickling treatment using a special pickling solution before forming the grooves, the specific heat and heat transfer coefficient of the precipitates on the steel sheet surface can be made closer to those of the base steel, thereby preventing the groove shape from becoming uneven due to differences in heat transfer. In addition, they discovered that by using a blower to blow air at a speed of 100 m/s or more when applying a heat source such as laser irradiation, it is possible to prevent components (dust) melted or evaporated from the steel sheet by the heat source from flying up and re-adhering to the steel sheet, laser, etc.
　本発明は上記知見に基づいて完成されたものである。本発明では、磁区細分化の為に形成された線状の溝の形状および溝内部の底面および溝内部の側面の表面粗さのＳａ値を一定の範囲内にコントロールすることで、方向性電磁鋼板の鉄損を更に低減する。 The present invention was completed based on the above findings. In the present invention, the iron loss of grain-oriented electrical steel sheets is further reduced by controlling the shape of the linear grooves formed to subdivide the magnetic domains and the Sa value of the surface roughness of the bottom and side surfaces inside the grooves within a certain range.
　本発明の要旨は、質量％で、Ｓｉ：２．５０～４．５０％、Ｍｎ：０．０１～０．１５％を含有し、残部がＦｅおよび不純物であり、圧延直角方向と０～３０°の角度をなす方向に延在する線状の溝が、２～１０ｍｍの間隔で形成された鋼板表面を有する鋼板を備える方向性電磁鋼板であって、前記溝の深さＤが１０～４０μｍであり、前記溝の幅Ｗが２０～２００μｍであり、前記溝内部の底面の表面粗さのＳａ底値が１．０～５．０μｍであり、前記溝内部の側面の表面粗さのＳａ側面値が１．０～５．０μｍである方向性電磁鋼板である。 The gist of the present invention is a grain-oriented electrical steel sheet comprising a steel sheet having a surface on which linear grooves extending in a direction forming an angle of 0 to 30° with a rolling perpendicular direction are formed at intervals of 2 to 10 mm, the steel sheet containing, by mass, 2.50 to 4.50% Si, 0.01 to 0.15% Mn, and the balance being Fe and impurities, wherein the groove has a depth D of 10 to 40 μm, a width W of 20 to 200 μm, a bottom value Sa of surface roughness of a bottom surface inside the groove being 1.0 to 5.0 μm, and a side value Sa of surface roughness of a side surface inside the groove being 1.0 to 5.0 μm.
　本発明によれば、形成される溝内部の表面粗さＳａが所定の範囲に制限されることにより、磁壁の移動がスムーズになり、ヒステリシス損が低減され、結果として鉄損が低減される。 In accordance with the present invention, the surface roughness Sa inside the formed groove is limited to a predetermined range, which allows the magnetic domain walls to move smoothly, reducing hysteresis loss and, as a result, iron loss.
図１は、本発明の方向性電磁鋼板の溝の断面図である。FIG. 1 is a cross-sectional view of a groove in a grain-oriented electrical steel sheet according to the present invention.
　以下に本発明の好適な実施の形態について詳細に説明する。なお、特に断らない限り、数値ＡおよびＢについて「Ａ～Ｂ」という表記は「Ａ以上Ｂ以下」を意味するものとする。かかる表記において数値Ｂのみに単位を付した場合には、当該単位が数値Ａにも適用されるものとする。 The preferred embodiment of the present invention will be described in detail below. Unless otherwise specified, the notation "A-B" for numerical values A and B means "greater than or equal to A and less than or equal to B." In such notations, when a unit is added only to numerical value B, the unit is also applied to numerical value A.
［鋼板の成分組成］
　まず、発明に係る方向性電磁鋼板に用いられる鋼板の成分組成について説明する。
なお、以下では特に断りのない限り、「％」との表記は「質量％」を表わすものとする。また、以下で説明する元素以外の鋼板の残部は、Ｆｅおよび不純物である。 [Steel plate composition]
First, the chemical composition of the steel sheet used in the grain-oriented electrical steel sheet according to the present invention will be described.
In the following, unless otherwise specified, the notation "%" represents "mass %." The balance of the steel sheet other than the elements described below is Fe and impurities.
　発明に係る方向性電磁鋼板に用いられる鋼板は、結晶方位を｛１１０｝＜００１＞方位（Ｇｏｓｓ方位）に集積させた集合組織に制御するために好ましい成分を含み、少なくとも、Ｓｉ：２．５０～４．５０％、Ｍｎ：０．０１～０．１５％を含有する。 The steel sheet used in the grain-oriented electrical steel sheet of the present invention contains components that are favorable for controlling the crystal orientation to a texture concentrated in the {110}<001> orientation (Goss orientation), and contains at least Si: 2.50-4.50% and Mn: 0.01-0.15%.
　（Ｓｉ：２．５０～４．５０％）
　Ｓｉ（ケイ素）の含有量は、２．５０～４．５０％である。Ｓｉは、鋼板の電気抵抗を高めることで、鉄損の原因の一つである渦電流損失を低減する。Ｓｉの含有量が２．５０％未満である場合、最終的な方向性電磁鋼板の渦電流損失を十分に抑制することが困難になるため好ましくない。Ｓｉの含有量が４．５０％超である場合、方向性電磁鋼板の加工性が低下するため好ましくない。したがって、Ｓｉの含有量は、２．５０～４．５０％であり、好ましくは、２．７０～４．００％である。 (Si: 2.50 to 4.50%)
The content of Si (silicon) is 2.50 to 4.50%. Si increases the electrical resistance of the steel sheet, thereby reducing eddy current loss, which is one of the causes of iron loss. If the content of Si is less than 2.50%, it is not preferable because it becomes difficult to sufficiently suppress the eddy current loss of the final grain-oriented electrical steel sheet. If the content of Si is more than 4.50%, it is not preferable because the workability of the grain-oriented electrical steel sheet decreases. Therefore, the content of Si is 2.50 to 4.50%, and preferably 2.70 to 4.00%.
　（Ｍｎ：０．０１～０．１５％）
　Ｍｎ（マンガン）の含有量は、０．０１～０．１５％である。Ｍｎは、二次再結晶に影響するインヒビターであるＭｎＳおよびＭｎＳｅなどを形成する。Ｍｎの含有量が０．０１％未満である場合、二次再結晶を生じさせるＭｎＳおよびＭｎＳｅの絶対量が不足するため好ましくない。Ｍｎの含有量が０．１５％超である場合、スラブ加熱時にＭｎの固溶が困難になるため好ましくない。また、Ｍｎの含有量が０．１５％超である場合、インヒビターであるＭｎＳおよびＭｎＳｅの析出サイズが粗大化し易く、インヒビターとしての最適サイズ分布が損なわれるため好ましくない。したがって、Ｍｎの含有量は、０．０１～０．１５％であり、好ましくは、０．０３～０．１３％である。 (Mn: 0.01 to 0.15%)
The content of Mn (manganese) is 0.01 to 0.15%. Mn forms MnS and MnSe, which are inhibitors that affect secondary recrystallization. If the content of Mn is less than 0.01%, the absolute amount of MnS and MnSe that cause secondary recrystallization is insufficient, which is not preferable. If the content of Mn is more than 0.15%, it is not preferable because it becomes difficult to dissolve Mn during slab heating. In addition, if the content of Mn is more than 0.15%, the precipitation size of MnS and MnSe, which are inhibitors, tends to become coarse, which is not preferable because the optimal size distribution as an inhibitor is impaired. Therefore, the content of Mn is 0.01 to 0.15%, preferably 0.03 to 0.13%.
　ＳｉおよびＭｎ以外の成分は、通常の方向性電磁鋼板に含まれている成分となることができる。
　例えば、Ｓｉ，Ｍｎ以外の成分として、質量％で、Ｃ：～０．０８５％以下、酸可溶性Ａｌ：～０．０６５％以下、Ｎ：～０．０１２％以下、Ｃｒ：～０．３０％以下、Ｃｕ：～０．４００％以下、Ｐ：～０．５００％以下、Ｓｎ：～０．３００％以下、Ｓｂ：～０．３００％以下、Ｎｉ：～１．０００％以下、Ｓ：～０．０１５％以下、Ｓｅ：～０．０１５％以下、Ｂｉ：～０．０２０％以下を含有することができる。なお、これらの成分の含有量は、純化焼鈍等を経た最終製品での含有量であるため、下限は限定されず、０％であってもよい。 The components other than Si and Mn may be the components contained in ordinary grain-oriented electrical steel sheets.
For example, as components other than Si and Mn, the following may be contained in mass %: C: up to 0.085%, acid-soluble Al: up to 0.065%, N: up to 0.012%, Cr: up to 0.30%, Cu: up to 0.400%, P: up to 0.500%, Sn: up to 0.300%, Sb: up to 0.300%, Ni: up to 1.000%, S: up to 0.015%, Se: up to 0.015%, and Bi: up to 0.020%. Note that the contents of these components are the contents in the final product that has been subjected to purification annealing and the like, so the lower limit is not limited and may be 0%.
　鋼板の上記成分以外の残部は、Ｆｅおよび不純物である。ここで、不純物元素とは、原材料に含まれる成分、または製造の過程で混入する成分であって、意図的に鋼板に含有させたものではない成分を指す。 The remainder of the steel plate other than the above components is Fe and impurities. Here, impurity elements refer to components contained in the raw materials or components mixed in during the manufacturing process, but not intentionally included in the steel plate.
　磁区細分化のために鋼板表面には、圧延方向と交差する方向に延在し且つ深さ方向が板厚方向となる溝が形成されている。なお、溝は、圧延方向と交差するように設けられていればよく、必ずしも、溝の延在方向と圧延方向とが直交している必要はないが、圧延直角方向と０～３０°の角度をなす方向に設けられている。また、溝は、板厚方向から視た場合（溝を平面視した場合）に、必ずしも直線形状を有していなくてもよく、弓状の形状を有してもよい。下記の溝の形状の測定は最終製品から酸洗等により少なくとも溝内部のグラス被膜および絶縁被膜を除去した後に行う。なお、溝は溝内部を含んでもよく、ここで溝内部とは、溝の輪郭によって画定され、鋼板の表面より窪んだ領域を指す。後述するように、溝は、溝内部の壁面（側面ともいう）および溝内部の底面を含んでもよい。 For magnetic domain refinement, grooves are formed on the surface of the steel sheet, which extend in a direction intersecting the rolling direction and whose depth direction is the sheet thickness direction. The grooves need not necessarily be perpendicular to the rolling direction as long as they are provided so as to intersect with the rolling direction, but are provided in a direction that forms an angle of 0 to 30° with the direction perpendicular to the rolling direction. The grooves do not necessarily have to have a linear shape when viewed from the sheet thickness direction (when the grooves are viewed from above), and may have an arched shape. The groove shape described below is measured after removing at least the glass coating and insulating coating from the inside of the groove from the final product by pickling or the like. The grooves may include the inside of the groove, and the inside of the groove refers to the area defined by the contour of the groove and recessed from the surface of the steel sheet. As described below, the grooves may include the wall surfaces (also called side surfaces) and the bottom surface of the inside of the groove.
　上記溝は、鋼板表面に、２～１０ｍｍの間隔で形成される。溝の間隔が２ｍｍ未満であると、磁区細分化効果が飽和し渦電流損の低減効果が得られにくくなる一方で、歪によってヒステリシス損は増加するため、鉄損は増加してしまい、好ましくない。溝の間隔が２０ｍｍを超えると磁区細分化効果が減少するため、鉄損改善効果が不足し、好ましくない。好ましい、溝の間隔は、３～７ｍｍである。 The grooves are formed on the surface of the steel sheet at intervals of 2 to 10 mm. If the groove spacing is less than 2 mm, the magnetic domain refinement effect saturates, making it difficult to obtain a reduction in eddy current loss, while hysteresis loss increases due to distortion, resulting in an increase in iron loss, which is undesirable. If the groove spacing exceeds 20 mm, the magnetic domain refinement effect decreases, resulting in insufficient iron loss improvement, which is undesirable. The preferred groove spacing is 3 to 7 mm.
　図１は、本発明の電磁鋼板の溝の断面図である。この断面図では溝内部は、台形に近い形状となっているが溝内部の形状は弓型になっていても構わない。本発明の電磁鋼板の一つの実施形態では、溝の深さＤは、１０μｍ～４０μｍの範囲である。深さＤが１０μｍ未満である場合、溝内部の壁面（溝内部の側面と称することがある）からの磁極の発生量が少なくなり、十分な鉄損低減効果が得られない。深さＤが４０μｍを超える場合、磁区は細分化されるが溝の形成による磁束密度の低下が大きくなり、十分な磁気特性が得られないことがある。好ましい深さは、１５μｍ～３０μｍである。 FIG. 1 is a cross-sectional view of a groove in an electromagnetic steel sheet of the present invention. In this cross-sectional view, the inside of the groove is shaped like a trapezoid, but the shape of the inside of the groove may also be arched. In one embodiment of the electromagnetic steel sheet of the present invention, the depth D of the groove is in the range of 10 μm to 40 μm. If the depth D is less than 10 μm, the amount of magnetic poles generated from the wall surface inside the groove (sometimes referred to as the side surface inside the groove) is small, and sufficient iron loss reduction effect cannot be obtained. If the depth D exceeds 40 μm, the magnetic domains are subdivided, but the reduction in magnetic flux density due to the formation of the groove is large, and sufficient magnetic properties may not be obtained. The preferred depth is 15 μm to 30 μm.
　（溝の深さＤの測定）
　本発明に係る「深さＤ」の測定方法は、以下のとおりである。
　電磁鋼板の任意の一つの溝を選択し、図１の溝の断面図に示す、溝の延在方向の手前側と奥側に３ｍｍ離れた任意の２点の溝の断面（Ａ）、（Ｂ）のそれぞれの最大深さのうち、深い方を深さｄ、浅い方を深さｄ’として、レーザー顕微鏡（ピンホールによる共焦点光学系を用いた３Ｄレーザー顕微鏡）を用いて測定した。深さＤは、これらの値の平均値である。 (Measurement of Groove Depth D)
The method for measuring the "depth D" according to the present invention is as follows.
An arbitrary groove in the electromagnetic steel sheet was selected, and the maximum depths of two arbitrary points (A) and (B) of the groove, which are 3 mm apart on the front side and the back side in the extension direction of the groove as shown in the cross-sectional view of the groove in Figure 1, were measured using a laser microscope (a 3D laser microscope using a confocal optical system with a pinhole), with the deeper one being depth d and the shallower one being depth d'. Depth D is the average value of these values.
　本発明にいう「溝の幅Ｗ」とは、図１においてｗ、ｗ’で示す部分である。溝の幅Ｗは、２０μｍ～２００μｍの範囲である。幅Ｗが２０μｍ未満である場合、溝内部の壁面（溝内部の側面）から漏れた磁束が反対側の溝内部の壁面（溝内部の側面）に入り、磁極の発生量が少なくなり、十分な鉄損低減効果が得られない。幅Ｗが２００μｍを超える場合、鉄損低減効果は飽和し、溝を形成する為に必要なレーザパワーが大きくなり製造コストが嵩むだけとなる。好ましい幅Ｗは、３０～１００μｍである。 The "groove width W" in this invention refers to the portions indicated by w and w' in Figure 1. The groove width W is in the range of 20 μm to 200 μm. If the width W is less than 20 μm, magnetic flux leaking from the wall surface inside the groove (side surface inside the groove) enters the wall surface inside the groove on the opposite side (side surface inside the groove), reducing the amount of magnetic pole generated and not achieving a sufficient iron loss reduction effect. If the width W exceeds 200 μm, the iron loss reduction effect saturates, and the laser power required to form the groove increases, resulting in increased manufacturing costs. The preferred width W is 30 to 100 μm.
　（溝の幅Ｗの測定）
　本発明に係る「溝の幅Ｗ」の測定方法は、以下のとおりである。
　電磁鋼板の任意の一つの溝を選択し、図１の溝の断面図に示す、溝の延在方向の手前側と奥側に３ｍｍ離れた任意の２点の溝の断面（Ａ）、（Ｂ）のそれぞれの溝の深さがそれぞれの溝の最大深さｄまたはｄ’の半分になる幅のうち、広い方をｗ、狭い方をｗ’として、レーザー顕微鏡（ピンホールによる共焦点光学系を用いた３Ｄレーザー顕微鏡）を用いて測定した。溝の幅Ｗは、これらの値の平均値である。 (Measurement of groove width W)
The method for measuring the "groove width W" according to the present invention is as follows.
An arbitrary groove of the electromagnetic steel sheet was selected, and the widths of the widths at which the depths of the grooves at two arbitrary points (A) and (B) located 3 mm apart on the front and back sides in the extension direction of the grooves, respectively, are half of the maximum depths d and d' of the respective grooves, were measured using a laser microscope (a 3D laser microscope using a pinhole confocal optical system), with the wider width being w and the narrower width being w', as shown in the cross-sectional view of the groove in Figure 1. The groove width W is the average value of these values.
　本発明にいう「溝内部の底面および溝内部の側面の表面粗さＳａ値」とは、図１において（Ａ）、（Ｂ）２点間の溝内部の底面および溝内部の側面の表面（三次元表面）粗さの算術平均高さＳａの値のことである。特に、溝内部の底面の表面粗さをＳａ底、溝内部の側面の表面粗さをＳａ側面と称することもある。表面（三次元表面）粗さの算術平均高さＳａの定義は、日本工業規格ＪＩＳＢ０６８１－６：２０１４（ＩＳＯ２５１７８－６：２０１０）「製品の幾何特性仕様（ＧＰＳ）―表面性状：三次元―第　６　部：表面性状測定方法の分類」にしたがう。本発明の方向性電磁鋼板では、それぞれのＳａは１．０～５．０μｍであり、好ましくは１．５～４．０μｍ、さらに好ましくは２．０～３．０μｍである。Ｓａが１．０μｍ未満である場合、磁気特性は問題ないが、製造技術的に実現が困難である。Ｓａが５．０μｍを超える場合、磁壁の移動がスムーズでなくなり、ヒステリシス損が増加し、十分な鉄損低減効果が得られない。 The "surface roughness Sa value of the bottom surface and the side surface of the groove" in the present invention refers to the arithmetic mean height Sa of the surface (three-dimensional surface) roughness of the bottom surface and the side surface of the groove between two points (A) and (B) in FIG. 1. In particular, the surface roughness of the bottom surface of the groove may be referred to as Sa bottom , and the surface roughness of the side surface of the groove may be referred to as Sa side . The definition of the arithmetic mean height Sa of the surface (three-dimensional surface) roughness is in accordance with the Japanese Industrial Standard JIS B0681-6:2014 (ISO25178-6:2010) "Product Geometric Characteristics Specification (GPS) - Surface Properties: Three Dimensions - Part 6: Classification of Surface Properties Measurement Methods". In the grain-oriented electrical steel sheet of the present invention, each Sa is 1.0 to 5.0 μm, preferably 1.5 to 4.0 μm, and more preferably 2.0 to 3.0 μm. When Sa is less than 1.0 μm, there is no problem with the magnetic properties, but it is difficult to realize from the viewpoint of manufacturing technology.When Sa exceeds 5.0 μm, the domain wall does not move smoothly, the hysteresis loss increases, and a sufficient iron loss reduction effect cannot be obtained.
　本発明において、溝内部の底面および溝内部の側面の表面粗さＳａを１．０～５．０μｍの範囲内とすることで鉄損低減効果が得られる理由は、表面粗さが所定の範囲にあることにより（溝の延在方向の手前側から奥側までの溝の断面積の変化が抑えられるので）、磁壁の移動がスムーズになり、ヒステリシス損の増加が抑えられたためであると思われる。 In the present invention, the reason that the effect of reducing iron loss is obtained by setting the surface roughness Sa of the bottom surface and side surfaces inside the groove within the range of 1.0 to 5.0 μm is believed to be that the surface roughness being within a specified range (the change in the cross-sectional area of the groove from the front to the back in the extension direction of the groove is suppressed), smooths the movement of the magnetic domain walls and suppresses the increase in hysteresis loss.
（溝内部の底面、溝内部の側面の表面粗さＳａの測定方法）
　レーザー顕微鏡（ピンホールによる共焦点光学系を用いた３Ｄレーザー顕微鏡）を用いて、Ｓａを測定した。電磁鋼板の任意の一つの溝を選択し、図１の溝の断面図に示す、溝の延在方向の手前側と奥側に３ｍｍ離れた任意の２点の溝の断面（Ａ）、（Ｂ）のそれぞれの最大深さの点ｄ、ｄ’をつないだ直線から直角方向（且つ電磁鋼板の板厚から直角方向）に片幅０．５μｍ（両幅１．０μｍ）の範囲を溝内部の底面とし、溝内部の底面の凹凸を、本発明の溝内部の底面の表面粗さＳａ底とする。また、両溝の断面（Ａ）、（Ｂ）のそれぞれの最大深さｄ、ｄ’の１／２の深さになる点（ｄ／２、ｄ’／２）のうち、最大深さに対して左右同じ側にある点をつないだ直線から直角方向（且つ電磁鋼板の板厚方向）に片幅０．５μｍ（両幅１．０μｍ）の範囲を溝内部の側面とし、溝内部の側面の凹凸のＳａ左とＳａ右を導出し、これらの値の平均値を溝内部の側面のＳａ側面とする。 (Method of measuring surface roughness Sa of bottom surface and side surface inside groove)
Sa was measured using a laser microscope (a 3D laser microscope using a pinhole confocal optical system). An arbitrary groove in the electromagnetic steel sheet was selected, and the bottom surface of the groove was determined to be a range of one side width of 0.5 μm (both widths of 1.0 μm) perpendicular to a straight line connecting the maximum depth points d and d' of the cross sections (A) and (B) of the groove at two points 3 mm apart on the front and back sides in the extension direction of the groove as shown in the cross-sectional view of the groove in FIG. 1 (and perpendicular to the sheet thickness of the electromagnetic steel sheet), and the unevenness of the bottom surface inside the groove is the surface roughness Sa bottom of the bottom surface inside the groove of the present invention. In addition, among the points (d/2, d'/2) that are 1/2 the maximum depths d, d' of the cross sections (A) and (B) of both grooves, the range of one side width 0.5 μm (both widths 1.0 μm) in the perpendicular direction (and in the thickness direction of the electromagnetic steel sheet) from the straight line connecting the points on the same side of the maximum depth is defined as the side inside the groove, and Sa left and Sa right of the unevenness of the side inside the groove are derived, and the average value of these values is defined as Sa side of the side inside the groove.
　参考用に、線形の表面粗さＲａについて説明する。「溝内部の底面および溝内部の側面の線形の表面粗さＲａ値」とは、図１において（Ａ）、（Ｂ）２点間の溝内部の底面および溝内部の側面の粗さ曲線の算術平均高さＲａの値のことである。粗さ曲線の算術平均高さＲａの定義は、日本工業規格ＪＩＳ Ｂ ０６０１（２０１３）にしたがう。 For reference, the linear surface roughness Ra will be explained. "The linear surface roughness Ra value of the bottom surface inside the groove and the side surface inside the groove" refers to the arithmetic mean height Ra of the roughness curve of the bottom surface inside the groove and the side surface inside the groove between two points (A) and (B) in Figure 1. The definition of the arithmetic mean height Ra of the roughness curve follows Japanese Industrial Standard JIS B 0601 (2013).
（溝内部の底面、溝内部の側面の表面粗さＲａの測定方法）
　レーザー顕微鏡（ピンホールによる共焦点光学系を用いた３Ｄレーザー顕微鏡）を用いて、各Ｒａを測定した。電磁鋼板の任意の一つの溝を選択し、図１の溝の断面図に示す、溝の方向の手前側と奥側に３ｍｍ離れた任意の２点の溝の断面（Ａ）、（Ｂ）のそれぞれの最大深さの点ｄ、ｄ’をつないだ直線の溝内部の底面の凹凸を、本発明の溝内部の底面の表面粗さＲａ底とする。また、両溝の断面（Ａ）、（Ｂ）のそれぞれの最大深さｄ、ｄ’の１／２の深さになる点（ｄ／２、ｄ’／２）のうち、最大深さに対して左右同じ側にある点をつないだ直線の溝内部の側面の凹凸のＲａ左とＲａ右を導出し、これらの値の平均値を溝内部の側面のＲａ側面とする。 (Method of measuring surface roughness Ra of bottom surface and side surface of groove)
Each Ra was measured using a laser microscope (a 3D laser microscope using a pinhole confocal optical system). An arbitrary groove of an electromagnetic steel sheet was selected, and the unevenness of the bottom surface inside the groove of a straight line connecting the maximum depth points d and d' of each of the cross sections (A) and (B) of the groove, which are 3 mm apart from each other in the direction of the groove, as shown in the cross section of the groove in FIG. 1, was taken as the surface roughness Ra bottom of the bottom surface inside the groove of the present invention. In addition, the Ra left and Ra right of the unevenness of the side surface inside the groove of a straight line connecting the points on the same left and right sides of the maximum depth among the points (d/2, d'/2) that are 1/2 the depth of the maximum depths d and d ' of each of the cross sections (A) and (B) of both grooves, were derived, and the average value of these values was taken as the Ra side surface of the side surface inside the groove.
［方向性電磁鋼板の製造方法］
　本発明の方向性電磁鋼板の製造工程を、冷延鋼板を得るまでの工程と、その後の磁区制御工程とに分けて説明する。 [Method of manufacturing grain-oriented electrical steel sheet]
The manufacturing process of the grain-oriented electrical steel sheet of the present invention will be described below by dividing it into a process for obtaining a cold-rolled steel sheet and a subsequent magnetic domain control process.
〔スラブから冷延鋼板を得るまでの工程］
　質量％で、Ｓｉ：２．５０％～４．５０％、Ｍｎ：０．０１％～０．１５％を含有し、残部がＦｅおよび不純物であるスラブに熱間圧延を施すことで、熱延鋼板を得る。
　次に、この熱延鋼板に酸洗を施すことで酸洗板を得るか、あるいはこの熱延鋼板に熱延板焼鈍をして熱延焼鈍板を得た後に、前記熱延焼鈍板に酸洗を施すことで酸洗板を得る。ここで使用する酸洗溶液は、Ｃｕ、Ｈｇ、Ａｇ、Ｐｂ、Ｃｄ、Ｃｏ、ＺｎおよびＮｉのうちから１種または２種以上を含有し、各元素の濃度の合計が酸洗溶液に対して０．０００１～０．１０００質量％以下であり、ｐＨが－１以上５以下である。酸洗溶液の液温は１５℃～１００℃であり、鋼板が酸洗溶液に浸漬される時間は５秒以上２００秒以下である。この酸洗工程により酸洗板を得て、そして、この酸洗板に冷間圧延を施して冷延鋼板を得る。 [Process from slab to cold-rolled steel sheet]
A slab containing, by mass%, 2.50% to 4.50% Si, 0.01% to 0.15% Mn, and the balance being Fe and impurities, is hot-rolled to obtain a hot-rolled steel sheet.
Next, the hot-rolled steel sheet is pickled to obtain a pickled sheet, or the hot-rolled steel sheet is annealed to obtain a hot-rolled annealed sheet, and then the hot-rolled annealed sheet is pickled to obtain a pickled sheet. The pickling solution used here contains one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn, and Ni, the total concentration of each element is 0.0001 to 0.1000 mass% or less with respect to the pickling solution, and the pH is -1 to 5. The temperature of the pickling solution is 15°C to 100°C, and the time for which the steel sheet is immersed in the pickling solution is 5 seconds to 200 seconds. A pickled sheet is obtained by this pickling process, and the pickled sheet is cold-rolled to obtain a cold-rolled steel sheet.
　［スラブの成分組成］
　発明に係る方向性電磁鋼板の製造に用いられるスラブの成分は、少なくとも、Ｓｉ：２．５０～４．５０％、Ｍｎ：０．０１～０．１５％を含有する。 [Slab composition]
The components of the slab used in the production of the grain-oriented electrical steel sheet according to the present invention contain at least Si: 2.50 to 4.50%, Mn: 0.01 to 0.15%.
　Ｓｉ（ケイ素）の含有量は、２．５０～４．５０％である。Ｓｉは、鋼板の電気抵抗を高めることで、鉄損の原因の一つである渦電流損失を低減する。Ｓｉの含有量が２．５０％未満である場合、最終的な方向性電磁鋼板の渦電流損失を十分に抑制することが困難になるため好ましくない。Ｓｉの含有量が４．５０％超である場合、方向性電磁鋼板の加工性が低下するため好ましくない。したがって、Ｓｉの含有量は、２．５０％～４．５０％であり、好ましくは、２．７０～４．００％である。 The Si (silicon) content is 2.50-4.50%. Si increases the electrical resistance of the steel sheet, thereby reducing eddy current loss, which is one of the causes of iron loss. If the Si content is less than 2.50%, it is not preferable because it becomes difficult to sufficiently suppress eddy current loss in the final grain-oriented electrical steel sheet. If the Si content is more than 4.50%, it is not preferable because the workability of the grain-oriented electrical steel sheet decreases. Therefore, the Si content is 2.50%-4.50%, and preferably 2.70-4.00%.
　Ｍｎ（マンガン）の含有量は、０．０１～０．１５％である。Ｍｎは、二次再結晶に影響するインヒビターであるＭｎＳおよびＭｎＳｅなどを形成する。Ｍｎの含有量が０．０１％未満である場合、二次再結晶を生じさせるＭｎＳおよびＭｎＳｅの絶対量が不足するため好ましくない。Ｍｎの含有量が０．１５％超である場合、スラブ加熱時にＭｎの固溶が困難になるため好ましくない。また、Ｍｎの含有量が０．１５％超である場合、インヒビターであるＭｎＳおよびＭｎＳｅの析出サイズが粗大化し易く、インヒビターとしての最適サイズ分布が損なわれるため好ましくない。したがって、Ｍｎの含有量は、０．０１～０．１５％であり、好ましくは、０．０３～０．１３％である。 The Mn (manganese) content is 0.01 to 0.15%. Mn forms MnS and MnSe, which are inhibitors that affect secondary recrystallization. If the Mn content is less than 0.01%, the absolute amount of MnS and MnSe that cause secondary recrystallization is insufficient, which is undesirable. If the Mn content is more than 0.15%, it is undesirable because it becomes difficult for Mn to form a solid solution when the slab is heated. Also, if the Mn content is more than 0.15%, it is undesirable because the precipitate size of MnS and MnSe, which are inhibitors, tends to become coarse, which impairs the optimal size distribution as an inhibitor. Therefore, the Mn content is 0.01 to 0.15%, and preferably 0.03 to 0.13%.
　ＳｉおよびＭｎ以外の成分は、以下の成分となることができる。
　例えば、Ｓｉ，Ｍｎ以外の成分として、質量％で、Ｃ：０．０２０～０．１００％、ＳおよびＳｅのうち１種または２種の合計：０．００１～０．０５０％、酸可溶性Ａｌ：０．０１０～０．０５０％、Ｎ：０．００２～０．０１５％、Ｃｒ：～０．３０％以下、Ｃｕ：～０．４００％以下、Ｐ：～０．５００％以下、Ｓｎ：～０．３００％以下、Ｓｂ：～０．３００％以下、Ｎｉ：～１．０００％以下、Ｂｉ：～０．０２０％以下を含有することができる。 The components other than Si and Mn can be the following components.
For example, as components other than Si and Mn, the alloy may contain, in mass %, C: 0.020 to 0.100%, one or two of S and Se: 0.001 to 0.050%, acid-soluble Al: 0.010 to 0.050%, N: 0.002 to 0.015%, Cr: up to 0.30% or less, Cu: up to 0.400% or less, P: up to 0.500% or less, Sn: up to 0.300% or less, Sb: up to 0.300% or less, Ni: up to 1.000% or less, and Bi: up to 0.020% or less.
　Ｃ（炭素）の含有量は、０．０２０～０．１００％である。Ｃには、種々の役割があるが、Ｃの含有量が０．０２０％未満である場合、スラブの加熱時に結晶粒径が過度に大きくなることで、最終的な方向性電磁鋼板の鉄損値を増大させるため好ましくない。Ｃの含有量が０．１００％超である場合、冷間圧延後の脱炭時に、脱炭時間が長時間になり、製造コストが増加するため好ましくない。また、Ｃの含有量が０．１００％超である場合、脱炭が不完全になり易く、最終的な方向性電磁鋼板において磁気時効を起こす可能性があるため好ましくない。したがって、Ｃの含有量は、０．０２０～０．１００％であり、好ましくは、０．０５０～０．０９０％である。 The C (carbon) content is 0.020-0.100%. C has various roles, but if the C content is less than 0.020%, the grain size becomes excessively large when the slab is heated, which increases the iron loss value of the final grain-oriented electrical steel sheet, which is not preferable. If the C content exceeds 0.100%, the decarburization time becomes long during decarburization after cold rolling, which increases the manufacturing cost, which is not preferable. Also, if the C content exceeds 0.100%, decarburization is likely to be incomplete, which is not preferable because it may cause magnetic aging in the final grain-oriented electrical steel sheet. Therefore, the C content is 0.020-0.100%, and preferably 0.050-0.090%.
　Ｓ（硫黄）およびＳｅ（セレン）の含有量は、合計で０．００１～０．０５０％である。ＳおよびＳｅは、上述したＭｎと共にインヒビターを形成する。ＳおよびＳｅは、２種ともスラブに含有されていてもよいが、少なくともいずれか１種がスラブに含有されていればよい。ＳおよびＳｅの含有量の合計が上記範囲を外れる場合、十分なインヒビター効果が得られないため好ましくない。したがって、ＳおよびＳｅの含有量は、合計で０．００１～０．０５０％であり、好ましくは、０．００１～０．０４０％である。 The total content of S (sulfur) and Se (selenium) is 0.001-0.050%. S and Se form inhibitors together with the above-mentioned Mn. Both S and Se may be contained in the slab, but it is sufficient that at least one of them is contained in the slab. If the total content of S and Se is outside the above range, it is not preferable because a sufficient inhibitor effect cannot be obtained. Therefore, the total content of S and Se is 0.001-0.050%, and preferably 0.001-0.040%.
　酸可溶性Ａｌ（酸可溶性アルミニウム）の含有量は、０．０１０～０．０５０％である。酸可溶性Ａｌは、高磁束密度の方向性電磁鋼板を製造するために必要なインヒビターを構成する。酸可溶性Ａｌの含有量が０．０１０％未満である場合、酸可溶性Ａｌが量的に不足し、インヒビター強度が不足するため好ましくない。酸可溶性Ａｌの含有量が０．０５０％超である場合、インヒビターとして析出するＡｌＮが粗大化し、インヒビター強度を低下させるため好ましくない。したがって、酸可溶性Ａｌの含有量は、０．０１０～０．０５０％であり、好ましくは、０．０１０～０．０４０％である。 The acid-soluble Al (acid-soluble aluminum) content is 0.010-0.050%. Acid-soluble Al constitutes an inhibitor necessary for producing grain-oriented electrical steel sheets with high magnetic flux density. If the acid-soluble Al content is less than 0.010%, the amount of acid-soluble Al is insufficient, and the inhibitor strength is insufficient, which is not preferable. If the acid-soluble Al content is more than 0.050%, the AlN that precipitates as an inhibitor becomes coarse, which is not preferable, as it reduces the inhibitor strength. Therefore, the acid-soluble Al content is 0.010-0.050%, and preferably 0.010-0.040%.
　Ｎ（窒素）の含有量は、０．００２～０．０１５％である。Ｎは、上述した酸可溶性Ａｌと共にインヒビターであるＡｌＮを形成する。Ｎの含有量が上記範囲を外れる場合、十分なインヒビター効果が得られないため好ましくない。したがって、Ｎの含有量は、０．００２～０．０１５％であり、好ましくは、０．００２～０．０１２％である。 The N (nitrogen) content is 0.002-0.015%. N forms AlN, an inhibitor, together with the acid-soluble Al mentioned above. If the N content is outside the above range, it is not preferable because a sufficient inhibitor effect cannot be obtained. Therefore, the N content is 0.002-0.015%, and preferably 0.002-0.012%.
　また、本実施形態に係る方向性電磁鋼板の製造に用いられるスラブは、上述した元素の他に、磁気特性向上のために、残部Ｆｅの一部に代えて、質量％で、Ｃｕ：０．４００％以下、Ｐ：０．５００％以下、Ｓｎ：０．３００％以下、Ｓｂ：０．３００％以下、Ｎｉ：１．０００％以下、Ｓ：０．０２５％以下、Ｓｅ：０．０２５％以下、Ｂｉ：０．０２０％以下からなる群から選択される１種又は２種以上を含有してもよい。一態様に係るスラブにおいては、質量％で、Ｃｒの含有量が０．０２％以上であってよく、Ｂｉの含有量が０．０００５％以上であってよく、Ｓｂの含有量が０．００５％以上であってよく、Ｓｅの含有量が０．００１％以上であってよく、Ｍｏの含有量が０．００５％以上であってよい。 In addition to the above elements, the slab used in the manufacture of the grain-oriented electrical steel sheet according to this embodiment may contain, in mass%, one or more elements selected from the group consisting of Cu: 0.400% or less, P: 0.500% or less, Sn: 0.300% or less, Sb: 0.300% or less, Ni: 1.000% or less, S: 0.025% or less, Se: 0.025% or less, and Bi: 0.020% or less, in place of a portion of the remaining Fe, in order to improve magnetic properties. In the slab according to one embodiment, the Cr content may be 0.02% or more, the Bi content may be 0.0005% or more, the Sb content may be 0.005% or more, the Se content may be 0.001% or more, and the Mo content may be 0.005% or more, in mass%.
　上記で説明した成分組成に調整された溶鋼を鋳造することで、スラブが形成される。なお、スラブの鋳造方法は、特に限定されない。また、研究開発において、真空溶解炉などで鋼塊が形成されても、上記成分について、スラブが形成された場合と同様の効果が確認できる。 A slab is formed by casting molten steel adjusted to the composition described above. The method of casting the slab is not particularly limited. In research and development, even if a steel ingot is formed in a vacuum melting furnace or the like, the same effects can be confirmed for the above-mentioned components as when a slab is formed.
［熱延鋼板とする工程］
　鋳造されたスラブを所定の温度で加熱し、加熱されたスラブは、熱間圧延されて熱延鋼板に加工される。加工後の熱延鋼板の板厚は、例えば、１．８ｍｍ～３．５ｍｍであってもよい。熱延鋼板の板厚が１．８ｍｍ未満である場合、熱間圧延後の鋼板温度が低温化し、鋼板中のＡｌＮの析出量が増加することで二次再結晶が不安定となって、最終的な板厚が０．２３ｍｍ以下の方向性電磁鋼板において磁気特性が低下するため好ましくない。熱延鋼板の板厚が３．５ｍｍ超である場合、冷間圧延の工程での圧延負荷が大きくなるため好ましくない。 [Process for producing hot-rolled steel sheet]
The cast slab is heated at a predetermined temperature, and the heated slab is hot-rolled to be processed into a hot-rolled steel sheet. The thickness of the hot-rolled steel sheet after processing may be, for example, 1.8 mm to 3.5 mm. If the thickness of the hot-rolled steel sheet is less than 1.8 mm, the steel sheet temperature after hot rolling becomes low, and the amount of AlN precipitated in the steel sheet increases, making secondary recrystallization unstable, which is not preferable because the magnetic properties of the grain-oriented electrical steel sheet having a final thickness of 0.23 mm or less are reduced. If the thickness of the hot-rolled steel sheet is more than 3.5 mm, the rolling load in the cold rolling process becomes large, which is not preferable.
　［ショットブラスト工程］
　酸洗処理の前に、ショットブラスト処理等の処理によって鋼板表面にひび割れ等の欠陥を導入して、その後の酸洗処理で、酸洗液が一定深さの範囲までに及ぶようにする。この目的は、析出物であるＭｎＳ等を、ＣｕＳ等で置換もしくはコーティングするために、鋼板の一定深さまで酸洗液を浸透させることである。これによりＭｎＳをＣｕＳ等で置換もしくはコーティングできるため、鋼板表層の伝熱係数を一定にすることができる。溝をレーザー照射等の熱源によって形成する場合、熱が均等に伝わりやすくなるので、溝内部の表面粗さＳａが所定の範囲に制限される。その結果、磁壁の移動がスムーズになり、ヒステリシス損が低減され、鉄損が低減される。
　鋼板表面にひび割れ等の欠陥を導入する方法としては、ショットブラスト以外にも、レベラー等を用いることができる。 [Shot blasting process]
Before the pickling treatment, defects such as cracks are introduced into the surface of the steel sheet by a treatment such as shot blasting, so that the pickling solution reaches a certain depth in the subsequent pickling treatment. The purpose of this is to make the pickling solution penetrate the steel sheet to a certain depth in order to replace or coat precipitates such as MnS with CuS. This allows MnS to be replaced or coated with CuS, so that the heat transfer coefficient of the steel sheet surface layer can be made constant. When the grooves are formed by a heat source such as laser irradiation, heat is easily transferred evenly, so that the surface roughness Sa inside the grooves is limited to a predetermined range. As a result, the movement of the domain walls becomes smooth, hysteresis loss is reduced, and iron loss is reduced.
As a method for introducing defects such as cracks into the surface of a steel sheet, a leveller or the like can be used in addition to shot blasting.
　ショットブラストの条件は、例えば、機械式の投射装置を用いて、硬度がＨｖ５００程度、φ１．５ｍｍ程度の鉄球を投射速度５０ｍ／ｓで毎分１０００ｋｇ投射する条件があるが酸洗溶液が浸透する微細な亀裂が鋼板に導入されれば条件は問わない。 The conditions for shot blasting include, for example, using a mechanical projector to project 1,000 kg of iron balls with a hardness of about Hv500 and a diameter of about 1.5 mm at a projection speed of 50 m/s per minute, but there are no restrictions as long as fine cracks are introduced into the steel plate that allow the pickling solution to penetrate.
［酸洗工程］
　続いて、加工された熱延鋼板を酸洗するか、または熱延板焼鈍を行って、熱延焼鈍板を得た後に、この熱延焼鈍板に酸洗を施す。 [Pickling process]
Subsequently, the processed hot-rolled steel sheet is pickled or hot-rolled sheet annealed to obtain a hot-rolled annealed sheet, which is then pickled.
　酸洗溶液は、Ｃｕ、Ｈｇ、Ａｇ、Ｐｂ、Ｃｄ、Ｃｏ、ＺｎおよびＮｉのうちから１種または２種以上を含有し、各元素の濃度の合計が酸洗溶液に対して０．０００１～０．１０００質量％であり、ｐＨが－１以上５以下である。酸洗溶液の液温は１５℃以上１００℃以下であり、鋼板が酸洗溶液に浸漬される時間は５秒以上２００秒以下である。 The pickling solution contains one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni, the total concentration of each element is 0.0001-0.1000 mass% of the pickling solution, and the pH is -1 or more and 5 or less. The temperature of the pickling solution is 15°C or more and 100°C or less, and the steel sheet is immersed in the pickling solution for 5 seconds or more and 200 seconds or less.
　酸洗溶液のＣｕ、Ｈｇ、Ａｇ、Ｐｂ、Ｃｄ、Ｃｏ、ＺｎおよびＮｉのうち１種または２種以上の濃度の合計が酸洗溶液に対して０．０００１質量％未満である場合、板厚方向のインヒビター制御（ＭｎＳ等を、ＣｕＳ等で置換もしくはコーティングすること）の効果が不十分となり好ましくない。酸洗溶液のＣｕ、Ｈｇ、Ａｇ、Ｐｂ、Ｃｄ、Ｃｏ、ＺｎおよびＮｉのうち１種または２種以上の濃度の合計が酸洗溶液に対して０．１０００質量％超である場合、磁気特性向上の効果が飽和することに加えて、酸洗溶液のコストが増大するので好ましくない。したがって、酸洗溶液のＣｕ、Ｈｇ、Ａｇ、Ｐｂ、Ｃｄ、Ｃｏ、ＺｎおよびＮｉのうち１種または２種以上の濃度の合計は、酸洗溶液に対して０．０００１～０．１０００質量％である。 If the total concentration of one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni in the pickling solution is less than 0.0001% by mass, the effect of inhibitor control in the thickness direction (substituting or coating MnS, etc. with CuS, etc.) becomes insufficient, which is not preferable. If the total concentration of one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni in the pickling solution exceeds 0.1000% by mass, the effect of improving magnetic properties becomes saturated and the cost of the pickling solution increases, which is not preferable. Therefore, the total concentration of one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni in the pickling solution is 0.0001 to 0.1000% by mass.
　酸洗溶液のｐＨが－１未満である場合、酸性が強くなり過ぎて酸洗溶液の取扱いが困難となるので好ましくない。酸洗溶液のｐＨが５超である場合、酸洗処理による板厚方向のインヒビター制御の効果が不十分となり好ましくない。したがって、酸洗溶液のｐＨは、－１以上５以下である。 If the pH of the pickling solution is less than -1, it is undesirable because the acidity becomes too strong and the solution becomes difficult to handle. If the pH of the pickling solution is more than 5, the effect of the pickling process in controlling inhibitors in the thickness direction becomes insufficient, which is undesirable. Therefore, the pH of the pickling solution is between -1 and 5.
　酸洗溶液の液温が１５℃未満である場合、酸洗処理による板厚方向のインヒビター制御の効果が不十分となり好ましくない。酸洗溶液の液温が１００℃超である場合、酸洗溶液の取扱いが困難となるので好ましくない。したがって、酸洗溶液の液温は１５℃以上１００℃以下である。 If the temperature of the pickling solution is less than 15°C, the effect of the pickling process in controlling inhibitors in the thickness direction will be insufficient, which is not preferable. If the temperature of the pickling solution is more than 100°C, it will be difficult to handle the pickling solution, which is also not preferable. Therefore, the temperature of the pickling solution should be 15°C or higher and 100°C or lower.
　酸洗処理において鋼板が酸洗溶液に浸漬される時間が５秒未満である場合、酸洗処理による板厚方向のインヒビター制御の効果が不十分となり好ましくない。酸洗処理において鋼板が酸洗溶液に浸漬される時間が２００秒超である場合、設備が長大となるので好ましくない。したがって、酸洗処理において鋼板が酸洗溶液に浸漬される時間は５秒以上２００秒以下である。 If the time during which the steel sheet is immersed in the pickling solution during the pickling process is less than 5 seconds, the effect of the pickling process in controlling inhibitors in the thickness direction will be insufficient, which is not preferable. If the time during which the steel sheet is immersed in the pickling solution during the pickling process exceeds 200 seconds, the equipment will become long and large, which is not preferable. Therefore, the time during which the steel sheet is immersed in the pickling solution during the pickling process is 5 seconds or more and 200 seconds or less.
　本願条件で酸洗を行った場合、鋼中の析出物であるＭｎＳ等がＣｕＳ等で置換もしくはコーティングされることで、析出物を含む鋼板表層の伝熱係数を一定にすることができる。これにより、溝を形成するときに、レーザー照射等の熱の効果を一定にできる。逆に、酸洗で十分に析出物が置換もしくはコーティングされないと、鋼板表層の伝熱係数のばらつきが大きく、溝内部の底面と溝内部の側面の表面粗さＳａが大きくなる。一方で酸洗時間や酸洗液濃度を一定以上にしても伝熱係数一定化の効果は飽和してＳａの更なる低減は見込めない。 When pickling is performed under the conditions of this application, the precipitates in the steel, such as MnS, are replaced or coated with CuS, etc., and the heat transfer coefficient of the steel sheet surface containing the precipitates can be made constant. This makes it possible to make the effect of heat from laser irradiation, etc., constant when forming grooves. Conversely, if the precipitates are not sufficiently replaced or coated by pickling, there will be large variations in the heat transfer coefficient of the steel sheet surface, and the surface roughness Sa of the bottom and side surfaces inside the grooves will increase. On the other hand, even if the pickling time or pickling solution concentration is set to a certain level or higher, the effect of stabilizing the heat transfer coefficient will saturate and no further reduction in Sa can be expected.
［冷延鋼板とする工程］
　熱延鋼板に酸洗を施した後、１回の冷間圧延、または中間焼鈍を挟んだ複数回の冷間圧延にて圧延することで、冷延鋼板に加工する。
　また、冷間圧延のパス間、圧延ロールスタンド間、または圧延中に、鋼板を、３００℃程度以下で加熱処理してもよい。このような場合、最終的な方向性電磁鋼板の磁気特性を向上させることができる。なお、熱延鋼板を、３回以上の冷間圧延によって圧延してもよいが、多数回の冷間圧延は、製造コストを増大させるため、熱延鋼板を、１回または２回の冷間圧延によって圧延することが好ましい。冷間圧延をゼンジミアミルなどのリバース圧延で行う場合、それぞれの冷間圧延におけるパス回数は、特に限定されないが、製造コストの観点から、９回以下が好ましい。
　以上、スラブから冷延鋼板を得るまでの工程を説明した。 [Process for producing cold-rolled steel sheet]
The hot-rolled steel sheet is subjected to pickling and then rolled by one cold rolling or multiple cold rolling with intermediate annealing therebetween to be processed into a cold-rolled steel sheet.
In addition, the steel sheet may be heat-treated at about 300° C. or less between passes of cold rolling, between rolling roll stands, or during rolling. In such a case, the magnetic properties of the final grain-oriented electrical steel sheet can be improved. The hot-rolled steel sheet may be rolled by three or more cold rolling passes, but since multiple cold rolling passes increase the manufacturing cost, it is preferable to roll the hot-rolled steel sheet by one or two cold rolling passes. When cold rolling is performed by reverse rolling such as a Sendzimir mill, the number of passes in each cold rolling pass is not particularly limited, but is preferably 9 passes or less from the viewpoint of manufacturing costs.
The process for obtaining a cold-rolled steel sheet from a slab has been described above.
　続いて、脱炭焼鈍を行う。冷延鋼板に対して、所定の温度条件（例えば７００～９００℃で１～３分間加熱する条件）の下で熱処理（すなわち、脱炭焼鈍処理）を実施する。脱炭焼鈍処理を実施すると、冷延鋼板において、炭素が所定量以下に低減され、一次再結晶組織が形成される。また、脱炭焼鈍では、冷延鋼板の表面に、シリカ（ＳｉＯ2）を主成分として含有する酸化物層が形成される。 Next, decarburization annealing is performed. The cold-rolled steel sheet is subjected to heat treatment (i.e., decarburization annealing) under a predetermined temperature condition (for example, heating at 700 to 900°C for 1 to 3 minutes). When the decarburization annealing is performed, the carbon in the cold-rolled steel sheet is reduced to a predetermined amount or less, and a primary recrystallization structure is formed. In addition, in the decarburization annealing, an oxide layer containing silica (SiO 2 ) as a main component is formed on the surface of the cold-rolled steel sheet.
　続いて、焼鈍分離剤塗布行う。この工程では、マグネシア（ＭｇＯ）を主成分として含有する焼鈍分離剤を、冷延鋼板の表面（酸化物層の表面）に塗布する。
　続いて、仕上焼鈍を行う、焼鈍分離剤が塗布された冷延鋼板に対して、所定の温度条件（例えば１１００～１３００℃で２０～２４時間加熱する条件）の下で熱処理（すなわち、仕上焼鈍処理）を実施する。仕上焼鈍処理を実施すると、二次再結晶が冷延鋼板に生じるとともに、冷延鋼板が純化される。その結果、上述の鋼板の化学組成を有し、結晶粒の磁化容易軸と圧延方向Ｘとが一致するように結晶方位が制御された鋼板が得られる。 Next, an annealing separator is applied to the surface of the cold-rolled steel sheet (the surface of the oxide layer).
Next, the cold-rolled steel sheet coated with the annealing separator is subjected to heat treatment (i.e., finish annealing) under a predetermined temperature condition (for example, heating at 1100 to 1300°C for 20 to 24 hours). When the finish annealing is performed, secondary recrystallization occurs in the cold-rolled steel sheet and the cold-rolled steel sheet is purified. As a result, a steel sheet is obtained that has the above-mentioned chemical composition of the steel sheet and has a crystal orientation controlled so that the magnetization easy axis of the crystal grains coincides with the rolling direction X.
　また、上記のような仕上焼鈍処理が実施されると、シリカを主成分として含有する酸化物層が、マグネシアを主成分として含有する焼鈍分離剤と反応して、鋼板の表面にフォルステライト（Ｍｇ2ＳｉＯ4）等の複合酸化物を含むグラス皮膜が形成される。仕上焼鈍工程では、鋼板がコイル状に巻かれた状態で仕上焼鈍処理が実施される。仕上焼鈍処理中に鋼板の表面にグラス皮膜が形成されることにより、コイル状に巻かれた鋼板に焼き付きが発生することを防止することができる。 Furthermore, when the above-mentioned finish annealing treatment is performed, the oxide layer containing silica as a main component reacts with the annealing separator containing magnesia as a main component to form a glass film containing composite oxides such as forsterite ( Mg2SiO4 ) on the surface of the steel sheet. In the finish annealing process, the finish annealing treatment is performed with the steel sheet wound in a coil shape. The formation of a glass film on the surface of the steel sheet during the finish annealing treatment can prevent the occurrence of seizure on the coiled steel sheet.
　［鋼板表面に線状の溝を形成する工程］
　その後に続く、レーザー照射工程で、グラス皮膜が形成された鋼板の表面（片面のみ）に対してレーザーを照射して、鋼板の表面に、圧延方向と交差する方向に延びる複数の溝を、圧延方向に沿って２～１０ｍｍの間隔で形成する。 [Step of forming linear grooves on steel sheet surface]
In the subsequent laser irradiation process, a laser is irradiated onto the surface (only one side) of the steel plate on which the glass coating has been formed, to form a plurality of grooves on the surface of the steel plate extending in a direction intersecting the rolling direction at intervals of 2 to 10 mm along the rolling direction.
　レーザー照射工程では、レーザー照射装置が、ポリゴンミラーの回転駆動によって、レーザー光を鋼板の表面に向けて照射すると共に、レーザー光を圧延直角方向と０～３０°の角度をなす方向に走査する。 In the laser irradiation process, the laser irradiation device rotates a polygon mirror to irradiate the surface of the steel plate with laser light, and scans the laser light in a direction that forms an angle of 0 to 30 degrees with the direction perpendicular to the rolling direction.
　レーザー光の照射と同時に、空気又は不活性ガス等のアシストガスが、レーザー光が照射される鋼板の部位に吹き付けられる。不活性ガスとは、例えば、窒素又はアルゴン等である。アシストガスは、レーザー照射によって鋼板から溶融又は蒸発した成分を除去する役割を担っている。アシストガスの吹き付けにより、レーザー光が上記溶融又は蒸発した成分によって阻害されずに鋼板に到達するため、溝が概ね安定的に形成される。
　ただし、アシストガスはレーザー照射スポットに限定的に吹き付けられているため、溝内部で生成する鋼板から溶融又は蒸発した成分（ダスト）がアシストガスに吹き上げられ、溝内部に滞留させない作用はあるものの、溝外部における鋼板やレーザーなどへの再付着は防止しにくい。これは溝の底面および側面の表面粗さＳａを変動させることがあり、所望の表面粗さＳａが得られないことがある。そのような再付着防止のため、溝外部に除去したダストを鋼板からより遠ざけるため、ブロワーガスが使用される。その観点から、ブロワーガスは鋼板のＴＤ方向（板幅方向）かつ鋼板面になるべく平行な方向（典型的には鋼板面を０度として±数度以内、または±１０度以内）に吹き付けることが望ましい。また、レーザー照射時のレーザー照射面にブロワーを用いて１００ｍ／ｓ以上、２００ｍ／ｓ以下の風速で風を送る。１００ｍ／ｓ以下では再付着の抑制効果が十分でなく、２００ｍ／ｓ超では風によって鋼板が振動してしまう。これにより、所望の表面粗さＳａを有する溝が形成される。 Simultaneously with the irradiation of the laser light, an assist gas such as air or an inert gas is sprayed onto the portion of the steel sheet to be irradiated with the laser light. The inert gas is, for example, nitrogen or argon. The assist gas plays a role in removing the components melted or evaporated from the steel sheet by the laser irradiation. By spraying the assist gas, the laser light reaches the steel sheet without being hindered by the melted or evaporated components, so that the grooves are formed generally stably.
However, since the assist gas is blown only onto the laser irradiation spot, the components (dust) melted or evaporated from the steel sheet generated inside the groove are blown up into the assist gas, and although there is an action of preventing the components from remaining inside the groove, it is difficult to prevent re-adhesion to the steel sheet, laser, etc. outside the groove. This may cause the surface roughness Sa of the bottom and side surfaces of the groove to fluctuate, and the desired surface roughness Sa may not be obtained. In order to prevent such re-adhesion, blower gas is used to move the dust removed outside the groove away from the steel sheet. From that viewpoint, it is desirable to blow the blower gas in the TD direction (sheet width direction) of the steel sheet and in a direction as parallel as possible to the steel sheet surface (typically within ± several degrees or ± 10 degrees with the steel sheet surface at 0 degrees). In addition, a blower is used to blow air at a speed of 100 m/s or more and 200 m/s or less onto the laser irradiation surface during laser irradiation. At 100 m/s or less, the effect of suppressing re-adhesion is insufficient, and at more than 200 m/s, the steel sheet vibrates due to the wind. As a result, grooves having the desired surface roughness Sa are formed.
　レーザー光源としては、例えばファイバレーザー、ＹＡＧレーザー、半導体レーザー、またはＣＯ2レーザー等の一般的に工業用に用いられる高出力レーザーを使用することができる。また、溝を安定的に形成することができさえすれば、パルスレーザー、または連続波レーザーをレーザー光源として使用してもよい。レーザー光としては、集光性が高く、溝の形成に適したシングルモードレーザーを用いることが好ましい。 As the laser light source, for example, a high-power laser generally used for industrial purposes, such as a fiber laser, a YAG laser, a semiconductor laser, or a CO2 laser, can be used. In addition, a pulsed laser or a continuous wave laser may be used as the laser light source as long as it can stably form a groove. As the laser light, it is preferable to use a single mode laser that has high light-collecting ability and is suitable for forming a groove.
　レーザー光の照射条件として、例えば、レーザー出力を２００Ｗ～３０００Ｗに、レーザー光の圧延方向における集光スポット径（すなわちレーザー出力の８６％を含む直径、以下８６％径と省略記載）を１０μｍ～２００μｍに設定し、レーザー光の板幅方向における集光スポット径（８６％径）を１０μｍ～１０００μｍに、レーザー走査速度を５ｍ／ｓ～５０ｍ／ｓ、レーザー走査ピッチ（間隔ＰＬ）を２ｍｍ～１０ｍｍに設定することが好ましい。１０～４０μｍの溝の深さＤが得られるように、これらのレーザー照射条件を適宜調整する。 As the laser light irradiation conditions, for example, it is preferable to set the laser output to 200W to 3000W, the focused spot diameter of the laser light in the rolling direction (i.e. the diameter containing 86% of the laser output, hereinafter abbreviated as 86% diameter) to 10μm to 200μm, the focused spot diameter of the laser light in the plate width direction (86% diameter) to 10μm to 1000μm, the laser scanning speed to 5m/s to 50m/s, and the laser scanning pitch (spacing PL) to 2mm to 10mm. These laser irradiation conditions are adjusted appropriately so that a groove depth D of 10 to 40μm is obtained.
　最後の絶縁皮膜形成工程では、上記のレーザー照射によって溝が形成された鋼板表面に対して、例えばコロイダルシリカおよびリン酸塩を含有する絶縁コーティング液が、グラス皮膜の上から塗布される。その後、所定の温度条件（例えば８４０～９２０℃）の下で熱処理が実施されることにより、最終的に、本発明に係る溝が形成された鋼板、グラス皮膜および絶縁皮膜を備える方向性電磁鋼板が得られる。 In the final insulating film forming process, an insulating coating liquid containing, for example, colloidal silica and phosphate is applied from above the glass film to the steel sheet surface on which grooves have been formed by the above-mentioned laser irradiation. Heat treatment is then carried out under specified temperature conditions (for example, 840 to 920°C), ultimately obtaining the steel sheet on which grooves have been formed, the glass film, and the insulating film according to the present invention.
　得られた方向性電磁鋼板に形成された溝の形状について、上述した測定方法を用いて、溝の深さＤ、溝の幅Ｗおよび溝内部の底面および溝内部の側面の表面粗さＳａを測定した。 The groove depth D, groove width W, and surface roughness Sa of the bottom and side surfaces inside the groove were measured for the shape of the grooves formed in the obtained grain-oriented electrical steel sheet using the measurement method described above.
　以下に、実施例を示しながら、本発明の方向性電磁鋼板について、より具体的に説明する。なお、以下に示す実施例は、本実施形態に係る方向性電磁鋼板のあくまでも一例に過ぎず、本実施形態に係る方向性電磁鋼板は、以下に示す実施例に限定されるものではない。 Below, the grain-oriented electrical steel sheet of the present invention will be described in more detail, showing examples. Note that the examples shown below are merely examples of the grain-oriented electrical steel sheet according to this embodiment, and the grain-oriented electrical steel sheet according to this embodiment is not limited to the examples shown below.
　方向性電磁鋼板が質量分率で、Ｓｉ：３．００％、Ｃ：０．０８０％、酸可溶性Ａｌ：０．０５０％、Ｎ：０．０１０％、Ｍｎ：０．１２％、Ｃｒ：０．０５％、Ｃｕ：０．０４０％、Ｐ：０．０１０％、Ｓｎ：０．０２０％、Ｓｂ：０．０１０％、Ｎｉ：０．００５％、Ｓ：０．００７％、Ｓｅ：０．００１％、を含有し、残部がＦｅおよび不純物からなる化学成分を有するように調製したスラブに対して熱間圧延が実施され、厚さ２．３ｍｍの熱延鋼板を得た。 The grain-oriented electrical steel sheet contained, by mass fraction, Si: 3.00%, C: 0.080%, acid-soluble Al: 0.050%, N: 0.010%, Mn: 0.12%, Cr: 0.05%, Cu: 0.040%, P: 0.010%, Sn: 0.020%, Sb: 0.010%, Ni: 0.005%, S: 0.007%, Se: 0.001%, with the remainder being Fe and impurities. The slab was then hot-rolled to obtain a hot-rolled steel sheet having a thickness of 2.3 mm.
　続いて、上記の熱延鋼板に対して、１０００℃で１分間加熱するという温度条件の下で焼鈍処理を実施した。 Next, the hot-rolled steel sheets were annealed at 1000°C for 1 minute.
　焼鈍処理の後、上述のショットブラスト処理によって鋼板表面にひび割れ等の欠陥を導入した。 After the annealing process, defects such as cracks were introduced into the steel plate surface by the above-mentioned shot blasting process.
　ショットブラストを実施した熱延鋼板の表面に下記に示す酸洗液および酸洗条件で、酸洗処理を実施した後、冷間圧延を実施して、厚さ０．２３ｍｍの冷延鋼板を得た。続いて、この冷延鋼板に対して、８００℃で２分間加熱するという温度条件の下で脱炭焼鈍処理を実施した後、マグネシア（ＭｇＯ）を主成分として含有する焼鈍分離剤を、冷延鋼板の表面に塗布した。 The surface of the shot-blasted hot-rolled steel sheet was pickled using the pickling solution and conditions shown below, and then cold-rolled to obtain a cold-rolled steel sheet with a thickness of 0.23 mm. Next, this cold-rolled steel sheet was subjected to a decarburization annealing process under temperature conditions of heating at 800°C for 2 minutes, and then an annealing separator containing magnesia (MgO) as its main component was applied to the surface of the cold-rolled steel sheet.
　酸洗液の成分、濃度、ｐＨ値、温度、浸漬時間を以下の範囲で、酸洗を行った。
（酸洗液の成分、濃度）Ｃｕ、Ｈｇ、Ａｇ、Ｐｂ、Ｃｄ、Ｃｏ、ＺｎおよびＮｉのうちから１種または２種以上を、各元素の濃度の合計が酸洗溶液に対して０．０００１～０．１０００質量％で、含有する。
（ｐＨ値）－１以上５以下
（温度）１５℃以上１００℃以下
（浸漬時間）５秒以上２００秒以下 Pickling was performed with the pickling solution components, concentration, pH value, temperature, and immersion time in the following ranges.
(Components and concentrations of the pickling solution) The pickling solution contains one or more of Cu, Hg, Ag, Pb, Cd, Co, Zn and Ni, with the total concentration of each element being 0.0001 to 0.1000 mass% based on the mass of the pickling solution.
(pH value) -1 to 5 (Temperature) 15°C to 100°C (Immersion time) 5 seconds to 200 seconds
　続いて、焼鈍分離剤が塗布された冷延鋼板に対して、１２００℃で２０時間加熱するという温度条件の下で仕上焼鈍処理を実施した。その結果、上述の化学組成を有し、結晶粒の磁化容易軸と圧延方向とが一致するように結晶方位が制御された、グラス皮膜が表面に形成された鋼板が得られた。 Then, the cold-rolled steel sheet coated with the annealing separator was subjected to a final annealing process under the temperature conditions of heating at 1200°C for 20 hours. As a result, a steel sheet was obtained with the above-mentioned chemical composition, a glass film formed on the surface, and a crystal orientation controlled so that the magnetization easy axis of the crystal grains coincided with the rolling direction.
　続いて、グラス皮膜が形成された鋼板の表面に対してレーザーを照射して、鋼板の表面に、圧延方向に交差する方向に延びる複数の溝を、圧延方向に沿って所定間隔で形成した。 Then, a laser was irradiated onto the surface of the steel plate on which the glass film had been formed, forming multiple grooves on the surface of the steel plate that extended in a direction intersecting the rolling direction and at predetermined intervals along the rolling direction.
　レーザー光の照射条件は、所望の溝の深さＤが得られるように、レーザー出力が２００Ｗ～３０００Ｗの範囲で、レーザー光の圧延方向における集光スポット径（８６％径）を１０μｍ～５００μｍの範囲で、レーザー光の板幅方向における集光スポット径（８６％径）を１０μｍ～１０００μｍの範囲で、レーザー走査速度を５ｍ／ｓ～５０ｍ／ｓの範囲で、レーザー走査ピッチ（間隔ＰＬ）を２ｍｍ～１０ｍｍの範囲に調整した。
　本発明例では、鋼板にレーザーを照射する際に、鋼板のレーザー照射面にブロワーを用いて鋼板のＴＤ方向（板幅方向）かつ鋼板面になるべく平行な方向に１００ｍ／ｓ以上の風速で風を送り、レーザー照射によって鋼板から溶融又は蒸発した成分が舞い上がって、鋼板やレーザーなどへの再付着を生じることを抑制した。 The conditions for the laser light irradiation were adjusted so that the desired groove depth D was obtained, with a laser output in the range of 200 W to 3000 W, a focused spot diameter (86% diameter) of the laser light in the rolling direction in the range of 10 μm to 500 μm, a focused spot diameter (86% diameter) of the laser light in the plate width direction in the range of 10 μm to 1000 μm, a laser scanning speed in the range of 5 m/s to 50 m/s, and a laser scanning pitch (spacing PL) in the range of 2 mm to 10 mm.
In the present invention, when a laser was irradiated onto a steel sheet, a blower was used to blow air at a speed of 100 m/s or more onto the laser irradiated surface of the steel sheet in the TD direction (sheet width direction) of the steel sheet and in a direction as parallel as possible to the steel sheet surface, thereby preventing components melted or evaporated from the steel sheet by laser irradiation from flying up and re-adhering to the steel sheet, the laser, etc.
　上記のように、溝が形成された鋼板に対して、コロイダルシリカおよびリン酸塩を含有する絶縁コーティング液をグラス皮膜の上から塗布した後、８５０℃で１分間加熱するという温度条件の下で熱処理を実施し、最終的に、溝が形成された鋼板、グラス皮膜および絶縁皮膜を備える方向性電磁鋼板が得られた。 As described above, an insulating coating liquid containing colloidal silica and phosphate was applied to the steel sheet with grooves on top of the glass film, and then heat treatment was carried out under temperature conditions of 850°C for 1 minute, ultimately resulting in a grain-oriented electrical steel sheet with grooves, a glass film, and an insulating film.
　比較例では、鋼板にレーザーを照射する際に、鋼板のレーザー照射面にブロワーを用いて、レーザー照射部分およびその周辺に風を当てることをしなかったか、または、酸洗条件を上記の範囲外で行った。 In the comparative examples, when the steel plate was irradiated with a laser, a blower was not used to blow air onto the laser-irradiated area and its surroundings, or the pickling conditions were outside the above range.
　形成された溝の形状について、上述した測定方法を用いて、溝の深さＤ、溝の幅Ｗ、溝内部の底面および溝内部の側面の表面粗さＳａを測定した。線形の粗さＲａおよび鉄損Ｗ１７／５０と併せて、測定結果を表１に示す。なお、良好な鉄損Ｗ１７／５０を０．７３（Ｗ／ｋｇ）以下として、この基準を満たすものに○（Good）を付した。鉄損は、ＪＩＳ　Ｃ２５５６：２０１５に準拠して測定した。 The groove shape was measured using the measurement method described above, including groove depth D, groove width W, and surface roughness Sa of the bottom and side surfaces inside the groove. The measurement results are shown in Table 1 along with the linear roughness Ra and iron loss W17/50. Good iron loss W17/50 is set to 0.73 (W/kg) or less, and those that meet this standard were marked with a circle (Good). Iron loss was measured in accordance with JIS C2556:2015.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　この結果から、実施例（発明例）では、所定条件で、ショットブラストおよび酸洗処理、並びにレーザー照射時のブロー処理を行ったことにより、溝内部の底面および溝内部の側面の表面粗さのＳａ値が一定の範囲内にコントロールされ、鉄損が比較例によりも更に低減されていることが分かる。 From these results, it can be seen that in the examples (invention examples), by performing shot blasting and pickling treatments, as well as blow treatment during laser irradiation under specified conditions, the Sa value of the surface roughness of the bottom surface and side surfaces inside the grooves was controlled within a certain range, and iron loss was further reduced compared to the comparative examples.

Claims (1)

  1. 　質量％で、Ｓｉ：２．５０～４．５０％、Ｍｎ：０．０１～０．１５％を含有し、残部がＦｅおよび不純物であり、圧延直角方向と０～３０°の角度をなす方向に延在する線状の溝が、２～１０ｍｍの間隔で形成された鋼板表面を有する鋼板を備える方向性電磁鋼板であって、
    　前記溝の深さＤが１０～４０μｍであり、
    　前記溝の幅Ｗが２０～２００μｍであり、
    　前記溝内部の底面の表面粗さのＳａ底値が１．０～５．０μｍであり、
    　前記溝内部の側面の表面粗さのＳａ側面値が１．０～５．０μｍである方向性電磁鋼板。     A grain-oriented electrical steel sheet comprising a steel sheet having a steel sheet surface on which linear grooves extending in a direction forming an angle of 0 to 30° with a rolling direction perpendicular to the rolling direction are formed at intervals of 2 to 10 mm, the steel sheet containing, by mass%, 2.50 to 4.50% Si, 0.01 to 0.15% Mn, and the balance being Fe and impurities,
    The depth D of the groove is 10 to 40 μm,
    The width W of the groove is 20 to 200 μm,
    The surface roughness Sa bottom value of the bottom surface inside the groove is 1.0 to 5.0 μm,
    The grain-oriented electrical steel sheet has a surface roughness Sa side value of the side surface inside the groove of 1.0 to 5.0 μm.
PCT/JP2023/041930 2022-11-22 2023-11-22 Grain-oriented electrical steel sheet WO2024111612A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007002334A (en) * 2005-05-09 2007-01-11 Nippon Steel Corp Low core loss grain-oriented electrical steel sheet and method for producing the same
WO2016171124A1 (en) * 2015-04-20 2016-10-27 新日鐵住金株式会社 Oriented magnetic steel plate
JP2022022494A (en) * 2020-06-24 2022-02-07 日本製鉄株式会社 Grain oriented electrical steel sheet

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007002334A (en) * 2005-05-09 2007-01-11 Nippon Steel Corp Low core loss grain-oriented electrical steel sheet and method for producing the same
WO2016171124A1 (en) * 2015-04-20 2016-10-27 新日鐵住金株式会社 Oriented magnetic steel plate
JP2022022494A (en) * 2020-06-24 2022-02-07 日本製鉄株式会社 Grain oriented electrical steel sheet

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